polyeq_5.miz



    begin

    reserve a,b for Complex;

    theorem :: POLYEQ_5:1

    

     Th1: (a * a) = (a |^ 2)

    proof

      

      thus (a * a) = ((a |^ 1) * a)

      .= (a |^ (1 + 1)) by NEWTON: 6

      .= (a |^ 2);

    end;

    theorem :: POLYEQ_5:2

    

     Th2: ((a * a) * a) = (a |^ 3)

    proof

      

      thus ((a * a) * a) = ((a |^ 2) * a) by Th1

      .= (a |^ (2 + 1)) by NEWTON: 6

      .= (a |^ 3);

    end;

    theorem :: POLYEQ_5:3

    

     Th3: (((a * a) * a) * a) = (a |^ 4)

    proof

      

      thus (((a * a) * a) * a) = ((a |^ 3) * a) by Th2

      .= (a |^ (3 + 1)) by NEWTON: 6

      .= (a |^ 4);

    end;

    theorem :: POLYEQ_5:4

    

     Th4: ((a - b) |^ 2) = (((a |^ 2) - ((2 * a) * b)) + (b |^ 2))

    proof

      

      thus ((a - b) |^ 2) = ((a - b) * (a - b)) by Th1

      .= (((a ^2 ) - ((2 * a) * b)) + (b ^2 ))

      .= (((a |^ 2) - ((2 * a) * b)) + (b * b)) by Th1

      .= (((a |^ 2) - ((2 * a) * b)) + (b |^ 2)) by Th1;

    end;

    theorem :: POLYEQ_5:5

    

     Th5: ((a - b) |^ 3) = ((((a |^ 3) - ((3 * (a |^ 2)) * b)) + ((3 * (b |^ 2)) * a)) - (b |^ 3))

    proof

      ((a - b) |^ (2 + 1)) = (((a - b) |^ 2) * (a - b)) by NEWTON: 6

      .= ((((a |^ 2) - ((2 * a) * b)) + (b |^ 2)) * (a - b)) by Th4

      .= (((((a |^ 2) * a) - ((a |^ 2) * b)) - ((((2 * a) * b) * a) - (((2 * a) * b) * b))) + (((b |^ 2) * a) - ((b |^ 2) * b)))

      .= (((((a |^ 2) * a) - ((a |^ 2) * b)) - ((((2 * a) * b) * a) - (((2 * a) * b) * b))) + (((b |^ 2) * a) - (b |^ (2 + 1)))) by NEWTON: 6

      .= ((((a |^ 3) - ((a |^ 2) * b)) - (((2 * (a * a)) * b) - (((2 * a) * b) * b))) + (((b |^ 2) * a) - (b |^ 3))) by NEWTON: 6

      .= ((((a |^ 3) - ((a |^ 2) * b)) - (((2 * ((a |^ 1) * a)) * b) - (((2 * a) * b) * b))) + (((b |^ 2) * a) - (b |^ 3)))

      .= ((((a |^ 3) - ((a |^ 2) * b)) - (((2 * (a |^ (1 + 1))) * b) - (((2 * a) * b) * b))) + (((b |^ 2) * a) - (b |^ 3))) by NEWTON: 6

      .= (((((a |^ 3) - ((3 * (a |^ 2)) * b)) + ((2 * (b * b)) * a)) + ((b |^ 2) * a)) - (b |^ 3))

      .= (((((a |^ 3) - ((3 * (a |^ 2)) * b)) + ((2 * ((b |^ 1) * b)) * a)) + ((b |^ 2) * a)) - (b |^ 3))

      .= (((((a |^ 3) - ((3 * (a |^ 2)) * b)) + ((2 * (b |^ (1 + 1))) * a)) + ((b |^ 2) * a)) - (b |^ 3)) by NEWTON: 6

      .= ((((a |^ 3) - ((3 * (a |^ 2)) * b)) + ((3 * (b |^ 2)) * a)) - (b |^ 3));

      hence thesis;

    end;

    theorem :: POLYEQ_5:6

    

     Th6: ((a - b) |^ 4) = (((((a |^ 4) - ((4 * (a |^ 3)) * b)) + ((6 * (a |^ 2)) * (b |^ 2))) - ((4 * (b |^ 3)) * a)) + (b |^ 4))

    proof

      ((a - b) |^ (3 + 1)) = (((a - b) |^ 3) * (a - b)) by NEWTON: 6

      .= (((((a |^ 3) - ((3 * (a |^ 2)) * b)) + ((3 * (b |^ 2)) * a)) - (b |^ 3)) * (a - b)) by Th5

      .= ((((((a |^ 3) * a) - ((a |^ 3) * b)) + (( - (((3 * (a |^ 2)) * b) * a)) + (((3 * (a |^ 2)) * b) * b))) + ((((3 * (b |^ 2)) * a) * a) - (((3 * (b |^ 2)) * a) * b))) + (( - ((b |^ 3) * a)) + ((b |^ 3) * b)))

      .= ((((((a |^ 3) * a) - ((a |^ 3) * b)) + (( - (((3 * (a |^ 2)) * b) * a)) + (((3 * (a |^ 2)) * b) * b))) + ((((3 * (b |^ 2)) * a) * a) - (((3 * (b |^ 2)) * a) * b))) + (( - ((b |^ 3) * a)) + (b |^ (3 + 1)))) by NEWTON: 6

      .= (((((a |^ 4) - ((a |^ 3) * b)) + (( - ((3 * ((a |^ 2) * a)) * b)) + (((3 * (a |^ 2)) * b) * b))) + ((((3 * (b |^ 2)) * a) * a) - (((3 * (b |^ 2)) * a) * b))) + (( - ((b |^ 3) * a)) + (b |^ 4))) by NEWTON: 6

      .= (((((a |^ 4) - ((a |^ 3) * b)) + (( - ((3 * (a |^ (2 + 1))) * b)) + (((3 * (a |^ 2)) * b) * b))) + ((((3 * (b |^ 2)) * a) * a) - (((3 * (b |^ 2)) * a) * b))) + (( - ((b |^ 3) * a)) + (b |^ 4))) by NEWTON: 6

      .= (((((a |^ 4) - ((a |^ 3) * b)) + (( - ((3 * (a |^ 3)) * b)) + ((3 * (a |^ 2)) * (b * b)))) + ((((3 * (b |^ 2)) * a) * a) - (((3 * (b |^ 2)) * a) * b))) + (( - ((b |^ 3) * a)) + (b |^ 4)))

      .= (((((a |^ 4) - ((a |^ 3) * b)) + (( - ((3 * (a |^ 3)) * b)) + ((3 * (a |^ 2)) * ((b |^ 1) * b)))) + ((((3 * (b |^ 2)) * a) * a) - (((3 * (b |^ 2)) * a) * b))) + (( - ((b |^ 3) * a)) + (b |^ 4)))

      .= (((((a |^ 4) - ((a |^ 3) * b)) + (( - ((3 * (a |^ 3)) * b)) + ((3 * (a |^ 2)) * (b |^ (1 + 1))))) + ((((3 * (b |^ 2)) * a) * a) - (((3 * (b |^ 2)) * a) * b))) + (( - ((b |^ 3) * a)) + (b |^ 4))) by NEWTON: 6

      .= (((((a |^ 4) - ((a |^ 3) * b)) + (( - ((3 * (a |^ 3)) * b)) + ((3 * (a |^ 2)) * (b |^ 2)))) + (((3 * (b |^ 2)) * (a * a)) - (((3 * (b |^ 2)) * a) * b))) + (( - ((b |^ 3) * a)) + (b |^ 4)))

      .= (((((a |^ 4) - ((a |^ 3) * b)) + (( - ((3 * (a |^ 3)) * b)) + ((3 * (a |^ 2)) * (b |^ 2)))) + (((3 * (b |^ 2)) * ((a |^ 1) * a)) - (((3 * (b |^ 2)) * b) * a))) + (( - ((b |^ 3) * a)) + (b |^ 4)))

      .= (((((a |^ 4) - ((a |^ 3) * b)) + (( - ((3 * (a |^ 3)) * b)) + ((3 * (a |^ 2)) * (b |^ 2)))) + (((3 * (b |^ 2)) * (a |^ (1 + 1))) - ((3 * ((b |^ 2) * b)) * a))) + (( - ((b |^ 3) * a)) + (b |^ 4))) by NEWTON: 6

      .= (((((a |^ 4) - ((a |^ 3) * b)) + (( - ((3 * (a |^ 3)) * b)) + ((3 * (a |^ 2)) * (b |^ 2)))) + (((3 * (b |^ 2)) * (a |^ 2)) - ((3 * (b |^ (2 + 1))) * a))) + (( - ((b |^ 3) * a)) + (b |^ 4))) by NEWTON: 6

      .= (((((a |^ 4) - ((4 * (a |^ 3)) * b)) + ((6 * (a |^ 2)) * (b |^ 2))) - ((4 * (b |^ 3)) * a)) + (b |^ 4));

      hence thesis;

    end;

    notation

      let n be Nat;

      let r be Real;

      synonym n -real-root r for n -root r;

    end

    definition

      let n be non zero Nat;

      let z be Complex;

      :: POLYEQ_5:def1

      func n -root z -> Complex equals ((n -real-root |.z.|) * (( cos (( Arg z) / n)) + (( sin (( Arg z) / n)) * <i> )));

      correctness ;

    end

    reserve z for Complex;

    reserve n0 for non zero Nat;

    theorem :: POLYEQ_5:7

    

     Th7: ((n0 -root z) |^ n0) = z

    proof

      reconsider n = n0 as Element of NAT by ORDINAL1:def 12;

      

      thus ((n0 -root z) |^ n0) = ((((n -real-root |.z.|) * ( cos ((( Arg z) + ((2 * PI ) * 0 )) / n))) + (((n -real-root |.z.|) * ( sin ((( Arg z) + ((2 * PI ) * 0 )) / n))) * <i> )) |^ n)

      .= z by POLYEQ_3: 34;

    end;

    theorem :: POLYEQ_5:8

    

     Th8: for r be Real st r >= 0 holds (n0 -root r) = (n0 -real-root r)

    proof

      let r be Real;

      reconsider r9 = r as Real;

      assume

       A1: r >= 0 ;

      then ( Arg r9) = 0 by COMPTRIG: 35;

      hence thesis by A1, COMPLEX1: 43, SIN_COS: 31;

    end;

    theorem :: POLYEQ_5:9

    

     Th9: for r be Real st r > 0 holds (n0 -root (z / r)) = ((n0 -root z) / (n0 -root r))

    proof

      let r be Real;

      reconsider r9 = (1 / r) as Real;

      reconsider n = n0 as Element of NAT by ORDINAL1:def 12;

      

       A1: n >= ( 0 + 1) by NAT_1: 13;

      assume

       A2: r > 0 ;

      then

       A3: |.r.| > 0 by COMPLEX1: 47;

      (z / r) = (z * (1 / r)) & ( Arg (z * r9)) = ( Arg z) by A2, COMPLEX2: 27, XCMPLX_1: 99;

      

      hence (n0 -root (z / r)) = ((n -real-root ( |.z.| / |.r.|)) * (( cos (( Arg z) / n)) + (( sin (( Arg z) / n)) * <i> ))) by COMPLEX1: 67

      .= (((n -real-root |.z.|) / (n -real-root |.r.|)) * (( cos (( Arg z) / n)) + (( sin (( Arg z) / n)) * <i> ))) by A3, A1, COMPLEX1: 46, POWER: 13

      .= ((( cos (( Arg z) / n)) + (( sin (( Arg z) / n)) * <i> )) / ((n -real-root |.r.|) / (n -real-root |.z.|))) by XCMPLX_1: 79

      .= (((n -real-root |.z.|) * (( cos (( Arg z) / n)) + (( sin (( Arg z) / n)) * <i> ))) / (n -real-root |.r.|)) by XCMPLX_1: 77

      .= ((n0 -root z) / (n -real-root r)) by A2, COMPLEX1: 43

      .= ((n0 -root z) / (n0 -root r)) by A2, Th8;

    end;

    theorem :: POLYEQ_5:10

    

     Th10: (z |^ 2) = a iff z = (2 -root a) or z = ( - (2 -root a))

    proof

      

       A1: a = ((2 -root a) |^ 2) by Th7

      .= ((2 -root a) * (2 -root a)) by Th1;

      hereby

        assume (z |^ 2) = a;

        then

         A2: (z * z) = a by Th1;

        assume not z = (2 -root a);

        then

         A3: (z - (2 -root a)) <> 0 ;

        assume not z = ( - (2 -root a));

        then (z + (2 -root a)) <> 0 ;

        then ((z - (2 -root a)) * (z + (2 -root a))) <> 0 by A3;

        hence contradiction by A1, A2;

      end;

      assume z = (2 -root a) or z = ( - (2 -root a));

      then ((z * z) - ((2 -root a) * (2 -root a))) = 0 ;

      hence (z |^ 2) = a by A1, Th1;

    end;

    begin

    reserve a0,a1,a2,s1,s2 for Complex;

    theorem :: POLYEQ_5:11

    

     Th11: a1 = ( - (s1 + s2)) & a0 = (s1 * s2) implies ((((z |^ 2) + (a1 * z)) + a0) = 0 iff z = s1 or z = s2)

    proof

      assume a1 = ( - (s1 + s2)) & a0 = (s1 * s2);

      

      then

       A1: ((z - s1) * (z - s2)) = (((z * z) + (a1 * z)) + a0)

      .= (((z |^ 2) + (a1 * z)) + a0) by Th1;

      hereby

        assume (((z |^ 2) + (a1 * z)) + a0) = 0 ;

        then

         A2: (z - s1) = 0 or (z - s2) = 0 by A1;

        assume not z = s1;

        hence z = s2 by A2;

      end;

      assume z = s1 or z = s2;

      hence (((z |^ 2) + (a1 * z)) + a0) = 0 by A1;

    end;

    theorem :: POLYEQ_5:12

    

     Th12: a2 <> 0 implies ((((a2 * (z |^ 2)) + (a1 * z)) + a0) = 0 iff z = (( - (a1 / (2 * a2))) + ((2 -root ( delta (a0,a1,a2))) / (2 * a2))) or z = (( - (a1 / (2 * a2))) - ((2 -root ( delta (a0,a1,a2))) / (2 * a2))))

    proof

      set s1 = (( - (a1 / (2 * a2))) + ((2 -root ( delta (a0,a1,a2))) / (2 * a2)));

      set s2 = (( - (a1 / (2 * a2))) - ((2 -root ( delta (a0,a1,a2))) / (2 * a2)));

      

       A1: ( - (s1 + s2)) = ((a1 / (2 * a2)) + (a1 / (2 * a2)))

      .= (((1 / 2) * (a1 / a2)) + (a1 / (2 * a2))) by XCMPLX_1: 103

      .= (((1 / 2) * (a1 / a2)) + ((1 / 2) * (a1 / a2))) by XCMPLX_1: 103

      .= (a1 / a2);

      assume

       A2: a2 <> 0 ;

      

      then (((a2 * (z |^ 2)) + (a1 * z)) + a0) = (((((a2 * (z |^ 2)) + (a1 * z)) + a0) / a2) * a2) by XCMPLX_1: 87

      .= (((((a2 * (z |^ 2)) / a2) + ((a1 * z) / a2)) + (a0 / a2)) * a2) by XCMPLX_1: 63

      .= ((((z |^ 2) + ((a1 * z) / a2)) + (a0 / a2)) * a2) by A2, XCMPLX_1: 89

      .= ((((z |^ 2) + (a1 * (z / a2))) + (a0 / a2)) * a2) by XCMPLX_1: 74

      .= ((((z |^ 2) + (z / (a2 / a1))) + (a0 / a2)) * a2) by XCMPLX_1: 81

      .= ((((z |^ 2) + ((a1 / a2) * z)) + (a0 / a2)) * a2) by XCMPLX_1: 79;

      then

       A3: (((a2 * (z |^ 2)) + (a1 * z)) + a0) = 0 iff (((z |^ 2) + ((a1 / a2) * z)) + (a0 / a2)) = 0 by A2;

      (s1 * s2) = (((a1 / (2 * a2)) * (a1 / (2 * a2))) - (((2 -root ( delta (a0,a1,a2))) / (2 * a2)) * ((2 -root ( delta (a0,a1,a2))) / (2 * a2))))

      .= (((a1 * a1) / ((2 * a2) * (2 * a2))) - (((2 -root ( delta (a0,a1,a2))) / (2 * a2)) * ((2 -root ( delta (a0,a1,a2))) / (2 * a2)))) by XCMPLX_1: 76

      .= (((a1 * a1) / ((4 * a2) * a2)) - (((2 -root ( delta (a0,a1,a2))) * (2 -root ( delta (a0,a1,a2)))) / ((2 * a2) * (2 * a2)))) by XCMPLX_1: 76

      .= (((a1 * a1) / ((4 * a2) * a2)) - (((2 -root ( delta (a0,a1,a2))) |^ 2) / ((2 * a2) * (2 * a2)))) by Th1

      .= (((a1 * a1) / ((4 * a2) * a2)) - (( delta (a0,a1,a2)) / ((2 * a2) * (2 * a2)))) by Th7

      .= (((a1 * a1) - ( delta (a0,a1,a2))) / ((4 * a2) * a2)) by XCMPLX_1: 120

      .= ((a0 * (4 * a2)) / (a2 * (4 * a2)))

      .= ((a0 / a2) * ((4 * a2) / (4 * a2))) by XCMPLX_1: 76

      .= ((a0 / a2) * 1) by A2, XCMPLX_1: 60

      .= (a0 / a2);

      hence thesis by A3, A1, Th11;

    end;

    begin

    reserve a3,x,q,r,s,s3 for Complex;

    theorem :: POLYEQ_5:13

    

     Th13: z = (x - (a2 / 3)) & q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) implies (((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff (((x |^ 3) + ((3 * q) * x)) - (2 * r)) = 0 )

    proof

      assume

       A1: z = (x - (a2 / 3));

      then

       A2: (3 * z) = ((3 * x) - a2);

      

       A3: ((3 * x) |^ 2) = ((3 |^ 2) * (x |^ 2)) by NEWTON: 7

      .= ((3 * 3) * (x |^ 2)) by Th1

      .= (9 * (x |^ 2));

      

       A4: ((3 * x) |^ 3) = ((3 |^ 3) * (x |^ 3)) by NEWTON: 7

      .= (((3 * 3) * 3) * (x |^ 3)) by Th2

      .= (27 * (x |^ 3));

      

       A5: (27 * (z |^ 3)) = (((3 * 3) * 3) * (z |^ 3))

      .= ((3 |^ 3) * (z |^ 3)) by Th2

      .= (((3 * x) - a2) |^ 3) by A2, NEWTON: 7

      .= ((((27 * (x |^ 3)) - ((3 * (9 * (x |^ 2))) * a2)) + ((3 * (a2 |^ 2)) * (3 * x))) - (a2 |^ 3)) by A4, A3, Th5

      .= ((((27 * (x |^ 3)) - ((27 * a2) * (x |^ 2))) + ((9 * (a2 |^ 2)) * x)) - (a2 |^ 3));

      assume

       A6: q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54);

      

       A7: ((27 * a1) * z) = (((27 * a1) * x) - ((9 * a2) * a1)) by A1;

      (((27 * 1) * a2) * (z |^ 2)) = ((((3 * a2) * (3 * 3)) * (1 * 1)) * (z |^ 2))

      .= (((3 * a2) * (3 |^ 2)) * (z |^ 2)) by Th1

      .= ((3 * a2) * ((3 |^ 2) * (z |^ 2)))

      .= ((3 * a2) * ((3 * z) |^ 2)) by NEWTON: 7

      .= ((3 * a2) * ((((3 * x) |^ 2) - ((2 * (3 * x)) * a2)) + (a2 |^ 2))) by A2, Th4

      .= ((3 * a2) * ((((3 * x) * (3 * x)) - ((2 * (3 * x)) * a2)) + (a2 |^ 2))) by Th1

      .= (((((27 * a2) * x) * x) - (((2 * (3 * x)) * a2) * (3 * a2))) + ((a2 |^ 2) * (3 * a2)))

      .= ((((27 * a2) * (x * x)) - ((18 * (a2 * a2)) * x)) + ((3 * a2) * (a2 * a2))) by Th1

      .= ((((27 * a2) * (x |^ 2)) - ((18 * (a2 * a2)) * x)) + (((3 * a2) * a2) * a2)) by Th1

      .= ((((27 * a2) * (x |^ 2)) - ((18 * (a2 |^ 2)) * x)) + (3 * ((a2 * a2) * a2))) by Th1

      .= ((((27 * a2) * (x |^ 2)) - ((18 * (a2 |^ 2)) * x)) + (3 * (a2 |^ 3))) by Th2;

      

      then (27 * ((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0)) = (((27 * (x |^ 3)) + ((( - (9 * (a2 |^ 2))) + (27 * a1)) * x)) + (((2 * (a2 |^ 3)) - ((9 * a2) * a1)) + (27 * a0))) by A5, A7

      .= (27 * (((x |^ 3) + ((3 * q) * x)) - (2 * r))) by A6;

      hence thesis;

    end;

    theorem :: POLYEQ_5:14

    

     Th14: a2 = ( - ((s1 + s2) + s3)) & a1 = (((s1 * s2) + (s1 * s3)) + (s2 * s3)) & a0 = ( - ((s1 * s2) * s3)) implies (((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff z = s1 or z = s2 or z = s3)

    proof

      assume a2 = ( - ((s1 + s2) + s3)) & a1 = (((s1 * s2) + (s1 * s3)) + (s2 * s3)) & a0 = ( - ((s1 * s2) * s3));

      

      then

       A1: (((z - s1) * (z - s2)) * (z - s3)) = (((((z * z) * z) + ((a2 * z) * z)) + (a1 * z)) + a0)

      .= ((((z |^ 3) + (a2 * (z * z))) + (a1 * z)) + a0) by Th2

      .= ((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0) by Th1;

      hereby

        assume ((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 ;

        then

         A2: ((z - s1) * (z - s2)) = 0 or (z - s3) = 0 by A1;

        assume ( not z = s1) & not z = s2;

        then (z - s1) <> 0 & (z - s2) <> 0 ;

        hence z = s3 by A2;

      end;

      assume z = s1 or z = s2 or z = s3;

      hence ((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 by A1;

    end;

    theorem :: POLYEQ_5:15

    q = (((3 * a1) - (a2 |^ 2)) / 9) & q <> 0 & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) implies (((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff z = ((s1 + s2) - (a2 / 3)) or z = ((( - ((s1 + s2) / 2)) - (a2 / 3)) + ((((s1 - s2) * (2 -root 3)) * <i> ) / 2)) or z = ((( - ((s1 + s2) / 2)) - (a2 / 3)) - ((((s1 - s2) * (2 -root 3)) * <i> ) / 2)))

    proof

      assume that

       A1: q = (((3 * a1) - (a2 |^ 2)) / 9) and

       A2: q <> 0 ;

      assume

       A3: r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54);

      set t = ((s1 + s2) / 2), d = ((s1 - s2) / 2);

      set x = (z + (a2 / 3));

      set x1 = (2 * t), x2 = (( - t) + ((d * (2 -root 3)) * <i> )), x3 = (( - t) - ((d * (2 -root 3)) * <i> ));

      

       A4: ( - ((x1 + x2) + x3)) = 0 ;

      assume

       A5: s = (2 -root ((q |^ 3) + (r |^ 2)));

      assume

       A6: s1 = (3 -root (r + s));

      

       A7: s1 <> 0

      proof

        assume s1 = 0 ;

        

        then

         A8: 0 = (s1 |^ 3) by NEWTON: 11

        .= (r + s) by A6, Th7;

        ((q |^ 3) + (r |^ 2)) = (s |^ 2) by A5, Th7

        .= (s * s) by Th1

        .= (( - s) * ( - s))

        .= (r |^ 2) by A8, Th1;

        then ((q * q) * q) = 0 by Th2;

        hence contradiction by A2;

      end;

      assume

       A9: s2 = ( - (q / s1));

      

      then

       A10: ((s2 * s2) * s2) = ( - (((q / s1) * (q / s1)) * (q / s1)))

      .= ( - (((q * q) / (s1 * s1)) * (q / s1))) by XCMPLX_1: 76

      .= ( - (((q * q) * q) / ((s1 * s1) * s1))) by XCMPLX_1: 76

      .= ( - (((q * q) * q) / ((3 -root (r + s)) |^ 3))) by A6, Th2

      .= ( - (((q * q) * q) / (r + s))) by Th7

      .= ( - ((q |^ 3) / (r + s))) by Th2;

      

       A11: ((s1 * s1) * s1) = (s1 |^ 3) by Th2

      .= (r + s) by A6, Th7;

      

       A12: (((x1 * x2) + (x1 * x3)) + (x2 * x3)) = (( - ((3 * t) * t)) - (((d * d) * ((2 -root 3) * (2 -root 3))) * ( - 1)))

      .= (( - ((3 * t) * t)) - (((d * d) * ((2 -root 3) |^ 2)) * ( - 1))) by Th1

      .= (( - ((3 * t) * t)) - (((d * d) * 3) * ( - 1))) by Th7

      .= (3 * (s1 * (q / s1))) by A9

      .= (3 * ((s1 * q) / s1)) by XCMPLX_1: 74

      .= (3 * q) by A7, XCMPLX_1: 89;

      ( - ((x1 * x2) * x3)) = (( - (2 * t)) * ((t * t) - (((d * d) * ((2 -root 3) * (2 -root 3))) * ( - 1))))

      .= (( - (2 * t)) * ((t * t) - (((d * d) * ((2 -root 3) |^ 2)) * ( - 1)))) by Th1

      .= (( - (2 * t)) * ((t * t) - (((d * d) * 3) * ( - 1)))) by Th7

      .= ( - ((r + s) - ((q |^ 3) / (r + s)))) by A11, A10

      .= ( - ((((r + s) * (r + s)) / (r + s)) - ((q |^ 3) / (r + s)))) by A11, A7, XCMPLX_1: 89

      .= ( - (((((r * r) + ((2 * s) * r)) + (s * s)) - (q |^ 3)) / (r + s))) by XCMPLX_1: 120

      .= ( - (((((r * r) + ((2 * s) * r)) + ((2 -root ((q |^ 3) + (r |^ 2))) |^ 2)) - (q |^ 3)) / (r + s))) by A5, Th1

      .= ( - (((((r * r) + ((2 * s) * r)) + ((q |^ 3) + (r |^ 2))) - (q |^ 3)) / (r + s))) by Th7

      .= ( - ((((r * r) + ((2 * s) * r)) + (r |^ 2)) / (r + s)))

      .= ( - ((((r * r) + ((2 * s) * r)) + (r * r)) / (r + s))) by Th1

      .= ( - (((2 * r) * (r + s)) / (r + s)))

      .= ( - (2 * r)) by A11, A7, XCMPLX_1: 89;

      then

       A13: ((((x |^ 3) + ( 0 * (x |^ 2))) + ((3 * q) * x)) + ( - (2 * r))) = 0 iff x = x1 or x = x2 or x = x3 by A4, A12, Th14;

      z = (x - (a2 / 3));

      then ((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff (((x |^ 3) + ((3 * q) * x)) - (2 * r)) = 0 by A1, A3, Th13;

      hence thesis by A13;

    end;

    theorem :: POLYEQ_5:16

    q = (((3 * a1) - (a2 |^ 2)) / 9) & q = 0 & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) implies (((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff z = (s1 - (a2 / 3)) or z = ((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2)) or z = ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2)))

    proof

      assume that

       A1: q = (((3 * a1) - (a2 |^ 2)) / 9) and

       A2: q = 0 ;

      set t = (s1 / 2);

      set x1 = (2 * t), x2 = (( - t) + ((t * (2 -root 3)) * <i> )), x3 = (( - t) - ((t * (2 -root 3)) * <i> ));

      

       A3: (((x1 * x2) + (x1 * x3)) + (x2 * x3)) = (( - ((3 * t) * t)) - (((t * t) * ((2 -root 3) * (2 -root 3))) * ( - 1)))

      .= (( - ((3 * t) * t)) - (((t * t) * ((2 -root 3) |^ 2)) * ( - 1))) by Th1

      .= (( - ((3 * t) * t)) - (((t * t) * 3) * ( - 1))) by Th7

      .= (3 * q) by A2;

      set x = (z + (a2 / 3));

      assume

       A4: r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54);

      assume

       A5: s1 = (3 -root (2 * r));

      

       A6: ( - ((x1 + x2) + x3)) = 0 ;

      

       A7: ((s1 * s1) * s1) = (s1 |^ 3) by Th2

      .= (2 * r) by A5, Th7;

      ( - ((x1 * x2) * x3)) = (( - (2 * t)) * ((t * t) - (((t * t) * ((2 -root 3) * (2 -root 3))) * ( - 1))))

      .= (( - (2 * t)) * ((t * t) - (((t * t) * ((2 -root 3) |^ 2)) * ( - 1)))) by Th1

      .= (( - (2 * t)) * ((t * t) - (((t * t) * 3) * ( - 1)))) by Th7

      .= ( - (2 * r)) by A7;

      then

       A8: ((((x |^ 3) + ( 0 * (x |^ 2))) + ((3 * q) * x)) + ( - (2 * r))) = 0 iff x = x1 or x = x2 or x = x3 by A6, A3, Th14;

      z = (x - (a2 / 3));

      then ((((z |^ 3) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff (((x |^ 3) + ((3 * q) * x)) - (2 * r)) = 0 by A1, A4, Th13;

      hence thesis by A8;

    end;

    definition

      let a0,a1,a2 be Complex;

      :: POLYEQ_5:def2

      func 1_root_of_cubic (a0,a1,a2) -> Complex means

      : Def2: ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & it = (s1 - (a2 / 3)) if ((3 * a1) - (a2 |^ 2)) = 0

      otherwise ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & it = ((s1 + s2) - (a2 / 3));

      existence

      proof

        set q = (((3 * a1) - (a2 |^ 2)) / 9), r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s = (2 -root ((q |^ 3) + (r |^ 2))), s1 = (3 -root (r + s)), s2 = ( - (q / s1)), IT = ((s1 + s2) - (a2 / 3));

        thus ((3 * a1) - (a2 |^ 2)) = 0 implies ex IT,r,s1 be Complex st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & IT = (s1 - (a2 / 3))

        proof

          set r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s1 = (3 -root (2 * r)), IT = (s1 - (a2 / 3));

          assume ((3 * a1) - (a2 |^ 2)) = 0 ;

          take IT, r, s1;

          thus thesis;

        end;

        assume ((3 * a1) - (a2 |^ 2)) <> 0 ;

        take IT, q, r, s, s1, s2;

        thus thesis;

      end;

      uniqueness ;

      correctness ;

      :: POLYEQ_5:def3

      func 2_root_of_cubic (a0,a1,a2) -> Complex means

      : Def3: ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & it = ((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2)) if ((3 * a1) - (a2 |^ 2)) = 0

      otherwise ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & it = ((( - ((s1 + s2) / 2)) - (a2 / 3)) + ((((s1 - s2) * (2 -root 3)) * <i> ) / 2));

      existence

      proof

        set q = (((3 * a1) - (a2 |^ 2)) / 9), r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s = (2 -root ((q |^ 3) + (r |^ 2))), s1 = (3 -root (r + s)), s2 = ( - (q / s1)), IT = ((( - ((s1 + s2) / 2)) - (a2 / 3)) + ((((s1 - s2) * (2 -root 3)) * <i> ) / 2));

        thus ((3 * a1) - (a2 |^ 2)) = 0 implies ex IT,r,s1 be Complex st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & IT = ((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2))

        proof

          set r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s1 = (3 -root (2 * r)), IT = ((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2));

          assume ((3 * a1) - (a2 |^ 2)) = 0 ;

          take IT, r, s1;

          thus thesis;

        end;

        assume ((3 * a1) - (a2 |^ 2)) <> 0 ;

        take IT, q, r, s, s1, s2;

        thus thesis;

      end;

      uniqueness ;

      correctness ;

      :: POLYEQ_5:def4

      func 3_root_of_cubic (a0,a1,a2) -> Complex means

      : Def4: ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & it = ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2)) if ((3 * a1) - (a2 |^ 2)) = 0

      otherwise ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & it = ((( - ((s1 + s2) / 2)) - (a2 / 3)) - ((((s1 - s2) * (2 -root 3)) * <i> ) / 2));

      existence

      proof

        set q = (((3 * a1) - (a2 |^ 2)) / 9), r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s = (2 -root ((q |^ 3) + (r |^ 2))), s1 = (3 -root (r + s)), s2 = ( - (q / s1)), IT = ((( - ((s1 + s2) / 2)) - (a2 / 3)) - ((((s1 - s2) * (2 -root 3)) * <i> ) / 2));

        thus ((3 * a1) - (a2 |^ 2)) = 0 implies ex IT,r,s1 be Complex st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & IT = ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2))

        proof

          set r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s1 = (3 -root (2 * r)), IT = ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2));

          assume ((3 * a1) - (a2 |^ 2)) = 0 ;

          take IT, r, s1;

          thus thesis;

        end;

        assume ((3 * a1) - (a2 |^ 2)) <> 0 ;

        take IT, q, r, s, s1, s2;

        thus thesis;

      end;

      uniqueness ;

      correctness ;

    end

    theorem :: POLYEQ_5:17

    

     Th17: ((( 1_root_of_cubic (a0,a1,a2)) + ( 2_root_of_cubic (a0,a1,a2))) + ( 3_root_of_cubic (a0,a1,a2))) = ( - a2)

    proof

      per cases ;

        suppose

         A1: ((3 * a1) - (a2 |^ 2)) = 0 ;

        then

         A2: ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & ( 3_root_of_cubic (a0,a1,a2)) = ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2)) by Def4;

        (ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & ( 1_root_of_cubic (a0,a1,a2)) = (s1 - (a2 / 3))) & ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & ( 2_root_of_cubic (a0,a1,a2)) = ((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2)) by A1, Def2, Def3;

        hence thesis by A2;

      end;

        suppose

         A3: ((3 * a1) - (a2 |^ 2)) <> 0 ;

        then

         A4: ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & ( 3_root_of_cubic (a0,a1,a2)) = ((( - ((s1 + s2) / 2)) - (a2 / 3)) - ((((s1 - s2) * (2 -root 3)) * <i> ) / 2)) by Def4;

        (ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & ( 1_root_of_cubic (a0,a1,a2)) = ((s1 + s2) - (a2 / 3))) & ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & ( 2_root_of_cubic (a0,a1,a2)) = ((( - ((s1 + s2) / 2)) - (a2 / 3)) + ((((s1 - s2) * (2 -root 3)) * <i> ) / 2)) by A3, Def2, Def3;

        hence thesis by A4;

      end;

    end;

    theorem :: POLYEQ_5:18

    

     Th18: (((( 1_root_of_cubic (a0,a1,a2)) * ( 2_root_of_cubic (a0,a1,a2))) + (( 1_root_of_cubic (a0,a1,a2)) * ( 3_root_of_cubic (a0,a1,a2)))) + (( 2_root_of_cubic (a0,a1,a2)) * ( 3_root_of_cubic (a0,a1,a2)))) = a1

    proof

      per cases ;

        suppose

         A1: ((3 * a1) - (a2 |^ 2)) = 0 ;

        set r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s1 = (3 -root (2 * r));

        

         A2: (ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & ( 2_root_of_cubic (a0,a1,a2)) = ((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2))) & ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & ( 3_root_of_cubic (a0,a1,a2)) = ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2)) by A1, Def3, Def4;

        

        thus (((( 1_root_of_cubic (a0,a1,a2)) * ( 2_root_of_cubic (a0,a1,a2))) + (( 1_root_of_cubic (a0,a1,a2)) * ( 3_root_of_cubic (a0,a1,a2)))) + (( 2_root_of_cubic (a0,a1,a2)) * ( 3_root_of_cubic (a0,a1,a2)))) = ((( 1_root_of_cubic (a0,a1,a2)) * (( 2_root_of_cubic (a0,a1,a2)) + ( 3_root_of_cubic (a0,a1,a2)))) + (( 2_root_of_cubic (a0,a1,a2)) * ( 3_root_of_cubic (a0,a1,a2))))

        .= (((s1 - (a2 / 3)) * (((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2)) + ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2)))) + (((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2)) * ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2)))) by A1, A2, Def2

        .= ((((( - (((3 * s1) * s1) / 4)) - ((a2 * s1) / 3)) + (((3 * a2) * a2) / 9)) + ((a2 * s1) / 3)) - (((((s1 * s1) * ((2 -root 3) * (2 -root 3))) * ( - 1)) / 2) / 2))

        .= ((( - (((3 * s1) * s1) / 4)) + ((a2 * a2) / 3)) - (((((s1 * s1) * ((2 -root 3) |^ 2)) * ( - 1)) / 2) / 2)) by Th1

        .= ((( - (((3 * s1) * s1) / 4)) + ((a2 * a2) / 3)) - (((((s1 * s1) * 3) * ( - 1)) / 2) / 2)) by Th7

        .= ((a2 |^ 2) / 3) by Th1

        .= a1 by A1;

      end;

        suppose

         A3: ((3 * a1) - (a2 |^ 2)) <> 0 ;

        set q = (((3 * a1) - (a2 |^ 2)) / 9), r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s = (2 -root ((q |^ 3) + (r |^ 2))), s1 = (3 -root (r + s)), s2 = ( - (q / s1));

        

         A4: s1 <> 0

        proof

          assume s1 = 0 ;

          

          then

           A5: 0 = (s1 |^ 3) by NEWTON: 11

          .= (r + s) by Th7;

          ((q |^ 3) + (r |^ 2)) = (s |^ 2) by Th7

          .= (s * s) by Th1

          .= (( - s) * ( - s))

          .= (r |^ 2) by A5, Th1;

          then ((q * q) * q) = 0 by Th2;

          hence contradiction by A3;

        end;

        

         A6: (ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & ( 2_root_of_cubic (a0,a1,a2)) = ((( - ((s1 + s2) / 2)) - (a2 / 3)) + ((((s1 - s2) * (2 -root 3)) * <i> ) / 2))) & ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & ( 3_root_of_cubic (a0,a1,a2)) = ((( - ((s1 + s2) / 2)) - (a2 / 3)) - ((((s1 - s2) * (2 -root 3)) * <i> ) / 2)) by A3, Def3, Def4;

        set t = (s1 + s2), d = (s1 - s2);

        

        thus (((( 1_root_of_cubic (a0,a1,a2)) * ( 2_root_of_cubic (a0,a1,a2))) + (( 1_root_of_cubic (a0,a1,a2)) * ( 3_root_of_cubic (a0,a1,a2)))) + (( 2_root_of_cubic (a0,a1,a2)) * ( 3_root_of_cubic (a0,a1,a2)))) = ((( 1_root_of_cubic (a0,a1,a2)) * (( 2_root_of_cubic (a0,a1,a2)) + ( 3_root_of_cubic (a0,a1,a2)))) + (( 2_root_of_cubic (a0,a1,a2)) * ( 3_root_of_cubic (a0,a1,a2))))

        .= (((t - (a2 / 3)) * (((( - (t / 2)) - (a2 / 3)) + (((d * (2 -root 3)) * <i> ) / 2)) + ((( - (t / 2)) - (a2 / 3)) - (((d * (2 -root 3)) * <i> ) / 2)))) + (((( - (t / 2)) - (a2 / 3)) + (((d * (2 -root 3)) * <i> ) / 2)) * ((( - (t / 2)) - (a2 / 3)) - (((d * (2 -root 3)) * <i> ) / 2)))) by A3, A6, Def2

        .= ((((( - (((3 * t) * t) / 4)) - ((a2 * t) / 3)) + (((3 * a2) * a2) / 9)) + ((a2 * t) / 3)) - ((((d * d) * ((2 -root 3) * (2 -root 3))) * ( - 1)) / 4))

        .= ((( - (((3 * t) * t) / 4)) + ((a2 * a2) / 3)) - ((((d * d) * ((2 -root 3) |^ 2)) * ( - 1)) / 4)) by Th1

        .= ((( - (((3 * t) * t) / 4)) + ((a2 * a2) / 3)) - ((((d * d) * 3) * ( - 1)) / 4)) by Th7

        .= (((3 * s1) * (q / s1)) + ((a2 * a2) / 3))

        .= ((3 * q) + ((a2 * a2) / 3)) by A4, XCMPLX_1: 90

        .= ((3 * q) + ((a2 |^ 2) / 3)) by Th1

        .= a1;

      end;

    end;

    theorem :: POLYEQ_5:19

    

     Th19: ((( 1_root_of_cubic (a0,a1,a2)) * ( 2_root_of_cubic (a0,a1,a2))) * ( 3_root_of_cubic (a0,a1,a2))) = ( - a0)

    proof

      per cases ;

        suppose

         A1: ((3 * a1) - (a2 |^ 2)) = 0 ;

        set r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s1 = (3 -root (2 * r));

        (ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & ( 2_root_of_cubic (a0,a1,a2)) = ((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2))) & ex r, s1 st r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s1 = (3 -root (2 * r)) & ( 3_root_of_cubic (a0,a1,a2)) = ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2)) by A1, Def3, Def4;

        

        hence ((( 1_root_of_cubic (a0,a1,a2)) * ( 2_root_of_cubic (a0,a1,a2))) * ( 3_root_of_cubic (a0,a1,a2))) = (((s1 - (a2 / 3)) * ((( - (s1 / 2)) - (a2 / 3)) + (((s1 * (2 -root 3)) * <i> ) / 2))) * ((( - (s1 / 2)) - (a2 / 3)) - (((s1 * (2 -root 3)) * <i> ) / 2))) by A1, Def2

        .= ((s1 - (a2 / 3)) * ((((s1 / 2) + (a2 / 3)) * ((s1 / 2) + (a2 / 3))) + ((((((2 -root 3) * (2 -root 3)) * s1) * s1) / 2) / 2)))

        .= ((s1 - (a2 / 3)) * ((((s1 / 2) + (a2 / 3)) * ((s1 / 2) + (a2 / 3))) + ((((((2 -root 3) |^ 2) * s1) * s1) / 2) / 2))) by Th1

        .= ((s1 - (a2 / 3)) * ((((s1 / 2) + (a2 / 3)) * ((s1 / 2) + (a2 / 3))) + ((((3 * s1) * s1) / 2) / 2))) by Th7

        .= (((s1 * s1) * s1) - (((((a2 * a2) * a2) / 3) / 3) / 3))

        .= ((s1 |^ 3) - (((a2 * a2) * a2) / 27)) by Th2

        .= ((2 * r) - (((a2 * a2) * a2) / 27)) by Th7

        .= ((((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 27) - ((a2 |^ 3) / 27)) by Th2

        .= (((((3 * a2) * a1) - (a2 |^ (2 + 1))) / 9) - a0)

        .= (((((3 * a2) * a1) - ((a2 |^ 2) * a2)) / 9) - a0) by NEWTON: 6

        .= ( - a0) by A1;

      end;

        suppose

         A2: ((3 * a1) - (a2 |^ 2)) <> 0 ;

        set q = (((3 * a1) - (a2 |^ 2)) / 9), r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54), s = (2 -root ((q |^ 3) + (r |^ 2))), s1 = (3 -root (r + s)), s2 = ( - (q / s1));

        

         A3: s1 <> 0

        proof

          assume s1 = 0 ;

          

          then

           A4: 0 = (s1 |^ 3) by NEWTON: 11

          .= (r + s) by Th7;

          ((q |^ 3) + (r |^ 2)) = (s |^ 2) by Th7

          .= (s * s) by Th1

          .= (( - s) * ( - s))

          .= (r |^ 2) by A4, Th1;

          then ((q * q) * q) = 0 by Th2;

          hence contradiction by A2;

        end;

        

         A5: ((s1 * s1) * s1) = (s1 |^ 3) by Th2

        .= (r + s) by Th7;

        

        then

         A6: ((r + s) - (((q * q) * q) / (r + s))) = ((((r + s) * (r + s)) / (r + s)) - (((q * q) * q) / (r + s))) by A3, XCMPLX_1: 89

        .= ((((r + s) * (r + s)) - ((q * q) * q)) / (r + s)) by XCMPLX_1: 120

        .= (((((r * r) + ((2 * r) * s)) + (s * s)) - (q |^ 3)) / (r + s)) by Th2

        .= (((((r * r) + ((2 * r) * s)) + (s |^ 2)) - (q |^ 3)) / (r + s)) by Th1

        .= (((((r * r) + ((2 * r) * s)) + ((q |^ 3) + (r |^ 2))) - (q |^ 3)) / (r + s)) by Th7

        .= ((((r * r) + ((2 * r) * s)) + (r |^ 2)) / (r + s))

        .= ((((r * r) + ((2 * r) * s)) + (r * r)) / (r + s)) by Th1

        .= (((2 * r) * (r + s)) / (r + s))

        .= (2 * r) by A5, A3, XCMPLX_1: 89;

        set t = (s1 + s2), d = (s1 - s2);

        

         A7: (s1 * s2) = ( - ((q / s1) * s1))

        .= ( - q) by A3, XCMPLX_1: 87;

        (ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & ( 2_root_of_cubic (a0,a1,a2)) = ((( - ((s1 + s2) / 2)) - (a2 / 3)) + ((((s1 - s2) * (2 -root 3)) * <i> ) / 2))) & ex q, r, s, s1, s2 st q = (((3 * a1) - (a2 |^ 2)) / 9) & r = (((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0)) / 54) & s = (2 -root ((q |^ 3) + (r |^ 2))) & s1 = (3 -root (r + s)) & s2 = ( - (q / s1)) & ( 3_root_of_cubic (a0,a1,a2)) = ((( - ((s1 + s2) / 2)) - (a2 / 3)) - ((((s1 - s2) * (2 -root 3)) * <i> ) / 2)) by A2, Def3, Def4;

        

        hence ((( 1_root_of_cubic (a0,a1,a2)) * ( 2_root_of_cubic (a0,a1,a2))) * ( 3_root_of_cubic (a0,a1,a2))) = (((t - (a2 / 3)) * ((( - (t / 2)) - (a2 / 3)) + (((d * (2 -root 3)) * <i> ) / 2))) * ((( - (t / 2)) - (a2 / 3)) - (((d * (2 -root 3)) * <i> ) / 2))) by A2, Def2

        .= ((t - (a2 / 3)) * ((((t / 2) + (a2 / 3)) * ((t / 2) + (a2 / 3))) + ((((((2 -root 3) * (2 -root 3)) * d) * d) / 2) / 2)))

        .= ((t - (a2 / 3)) * ((((t / 2) + (a2 / 3)) * ((t / 2) + (a2 / 3))) + ((((((2 -root 3) |^ 2) * d) * d) / 2) / 2))) by Th1

        .= ((t - (a2 / 3)) * ((((t / 2) + (a2 / 3)) * ((t / 2) + (a2 / 3))) + ((((3 * d) * d) / 2) / 2))) by Th7

        .= (((((s1 * s1) * s1) + ((s2 * s2) * s2)) + ((a2 * ((4 * s1) * s2)) / 4)) - (((a2 * a2) * a2) / 27))

        .= ((((s1 |^ 3) + ((s2 * s2) * s2)) + (a2 * (s1 * s2))) - (((a2 * a2) * a2) / 27)) by Th2

        .= ((((s1 |^ 3) + ((( - (q / s1)) * ( - (q / s1))) * ( - (q / s1)))) + (a2 * ( - q))) - (((a2 * a2) * a2) / 27)) by A7

        .= ((((s1 |^ 3) - (((q / s1) * (q / s1)) * (q / s1))) - (a2 * q)) - (((a2 * a2) * a2) / 27))

        .= ((((s1 |^ 3) - (((q * q) / (s1 * s1)) * (q / s1))) - (a2 * q)) - (((a2 * a2) * a2) / 27)) by XCMPLX_1: 76

        .= ((((s1 |^ 3) - (((q * q) * q) / ((s1 * s1) * s1))) - (a2 * q)) - (((a2 * a2) * a2) / 27)) by XCMPLX_1: 76

        .= ((((s1 |^ 3) - (((q * q) * q) / (s1 |^ 3))) - (a2 * q)) - (((a2 * a2) * a2) / 27)) by Th2

        .= ((((s1 |^ 3) - (((q * q) * q) / (r + s))) - (a2 * q)) - (((a2 * a2) * a2) / 27)) by Th7

        .= ((((r + s) - (((q * q) * q) / (r + s))) - (a2 * q)) - (((a2 * a2) * a2) / 27)) by Th7

        .= ((((2 * ((((9 * a2) * a1) - (2 * (a2 |^ 3))) - (27 * a0))) / 54) - (a2 * q)) - ((a2 |^ 3) / 27)) by A6, Th2

        .= ((((((9 * a2) * a1) - (3 * (a2 |^ 3))) / 27) - (a2 * q)) - a0)

        .= ((((((9 * a2) * a1) - (3 * ((a2 * a2) * a2))) / 27) - (a2 * q)) - a0) by Th2

        .= ((((a2 * ((3 * a1) - (a2 * a2))) / 9) - (a2 * q)) - a0)

        .= ((((a2 * ((3 * a1) - (a2 |^ 2))) / 9) - (a2 * q)) - a0) by Th1

        .= ( - a0);

      end;

    end;

    theorem :: POLYEQ_5:20

    a3 <> 0 implies (((((a3 * (z |^ 3)) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff z = ( 1_root_of_cubic ((a0 / a3),(a1 / a3),(a2 / a3))) or z = ( 2_root_of_cubic ((a0 / a3),(a1 / a3),(a2 / a3))) or z = ( 3_root_of_cubic ((a0 / a3),(a1 / a3),(a2 / a3))))

    proof

      assume

       A1: a3 <> 0 ;

      set s3 = ( 3_root_of_cubic ((a0 / a3),(a1 / a3),(a2 / a3)));

      set s2 = ( 2_root_of_cubic ((a0 / a3),(a1 / a3),(a2 / a3)));

      set s1 = ( 1_root_of_cubic ((a0 / a3),(a1 / a3),(a2 / a3)));

      ( - (a2 / a3)) = ((s1 + s2) + s3) by Th17;

      then

       A2: (a2 / a3) = ( - ((s1 + s2) + s3));

      ( - (a0 / a3)) = ((s1 * s2) * s3) by Th19;

      then

       A3: (a0 / a3) = ( - ((s1 * s2) * s3));

      (((((z |^ 3) + ((a2 / a3) * (z |^ 2))) + ((a1 / a3) * z)) + (a0 / a3)) * a3) = ((((a3 * (z |^ 3)) + (((a2 / a3) * a3) * (z |^ 2))) + (((a1 / a3) * a3) * z)) + ((a0 / a3) * a3))

      .= ((((a3 * (z |^ 3)) + (((a2 / a3) * a3) * (z |^ 2))) + (((a1 / a3) * a3) * z)) + a0) by A1, XCMPLX_1: 87

      .= ((((a3 * (z |^ 3)) + (((a2 / a3) * a3) * (z |^ 2))) + (a1 * z)) + a0) by A1, XCMPLX_1: 87

      .= ((((a3 * (z |^ 3)) + (a2 * (z |^ 2))) + (a1 * z)) + a0) by A1, XCMPLX_1: 87;

      then

       A4: ((((z |^ 3) + ((a2 / a3) * (z |^ 2))) + ((a1 / a3) * z)) + (a0 / a3)) = 0 iff ((((a3 * (z |^ 3)) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 by A1;

      (a1 / a3) = (((s1 * s2) + (s1 * s3)) + (s2 * s3)) by Th18;

      hence thesis by A4, A2, A3, Th14;

    end;

    begin

    reserve a4,p,s4 for Complex;

    theorem :: POLYEQ_5:21

    

     Th21: z = (x - (a3 / 4)) & p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) implies ((((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff ((((x |^ 4) + ((4 * p) * (x |^ 2))) + ((8 * q) * x)) + (4 * r)) = 0 )

    proof

      assume

       A1: z = (x - (a3 / 4));

      then

       A2: (4 * z) = ((4 * x) - a3);

      

       A3: (16 * (z |^ 2)) = ((4 * 4) * (z |^ 2))

      .= ((4 |^ 2) * (z |^ 2)) by Th1

      .= ((4 * z) |^ 2) by NEWTON: 7

      .= ((((4 * x) |^ 2) - ((2 * (4 * x)) * a3)) + (a3 |^ 2)) by A2, Th4

      .= ((((4 * x) * (4 * x)) - ((2 * (4 * x)) * a3)) + (a3 |^ 2)) by Th1

      .= (((16 * (x * x)) - ((8 * x) * a3)) + (a3 |^ 2))

      .= (((16 * (x |^ 2)) - ((8 * x) * a3)) + (a3 |^ 2)) by Th1;

      

       A4: ((4 * x) |^ 3) = ((4 |^ 3) * (x |^ 3)) by NEWTON: 7

      .= (((4 * 4) * 4) * (x |^ 3)) by Th2

      .= (64 * (x |^ 3));

      

       A5: ((4 * x) |^ 2) = ((4 |^ 2) * (x |^ 2)) by NEWTON: 7

      .= ((4 * 4) * (x |^ 2)) by Th1

      .= (16 * (x |^ 2));

      

       A6: ((4 * a3) * (64 * (z |^ 3))) = ((4 * a3) * (((4 * 4) * 4) * (z |^ 3)))

      .= ((4 * a3) * ((4 |^ 3) * (z |^ 3))) by Th2

      .= ((4 * a3) * (((4 * x) - a3) |^ 3)) by A2, NEWTON: 7

      .= ((4 * a3) * ((((64 * (x |^ 3)) - ((3 * (16 * (x |^ 2))) * a3)) + ((3 * (a3 |^ 2)) * (4 * x))) - (a3 |^ 3))) by A4, A5, Th5

      .= (((((256 * a3) * (x |^ 3)) - ((192 * (a3 * a3)) * (x |^ 2))) + ((48 * ((a3 |^ 2) * a3)) * x)) - (4 * ((a3 |^ 3) * a3)))

      .= (((((256 * a3) * (x |^ 3)) - ((192 * (a3 |^ 2)) * (x |^ 2))) + ((48 * ((a3 |^ 2) * a3)) * x)) - (4 * ((a3 |^ 3) * a3))) by Th1

      .= (((((256 * a3) * (x |^ 3)) - ((192 * (a3 |^ 2)) * (x |^ 2))) + ((48 * (a3 |^ (2 + 1))) * x)) - (4 * ((a3 |^ 3) * a3))) by NEWTON: 6

      .= (((((256 * a3) * (x |^ 3)) - ((192 * (a3 |^ 2)) * (x |^ 2))) + ((48 * (a3 |^ 3)) * x)) - (4 * (a3 |^ (3 + 1)))) by NEWTON: 6

      .= (((((256 * a3) * (x |^ 3)) - ((192 * (a3 |^ 2)) * (x |^ 2))) + ((48 * (a3 |^ 3)) * x)) - (4 * (a3 |^ 4)));

      

       A7: ((4 * x) |^ 4) = ((4 |^ 4) * (x |^ 4)) by NEWTON: 7

      .= ((((4 * 4) * 4) * 4) * (x |^ 4)) by Th3

      .= (256 * (x |^ 4));

      

       A8: (256 * (z |^ 4)) = ((((4 * 4) * 4) * 4) * (z |^ 4))

      .= ((4 |^ 4) * (z |^ 4)) by Th3

      .= (((4 * x) - a3) |^ 4) by A2, NEWTON: 7

      .= (((((256 * (x |^ 4)) - ((4 * (64 * (x |^ 3))) * a3)) + ((6 * (16 * (x |^ 2))) * (a3 |^ 2))) - ((4 * (a3 |^ 3)) * (4 * x))) + (a3 |^ 4)) by A7, A4, A5, Th6

      .= (((((256 * (x |^ 4)) - ((256 * (x |^ 3)) * a3)) + ((96 * (x |^ 2)) * (a3 |^ 2))) - ((16 * (a3 |^ 3)) * x)) + (a3 |^ 4));

      assume

       A9: p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024);

      (256 * (((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0)) = (((((256 * (z |^ 4)) + ((4 * a3) * (64 * (z |^ 3)))) + ((16 * a2) * (16 * (z |^ 2)))) + ((64 * a1) * (4 * z))) + (256 * a0))

      .= (((((((((256 * (x |^ 4)) - ((256 * (x |^ 3)) * a3)) + ((96 * (x |^ 2)) * (a3 |^ 2))) - ((16 * (a3 |^ 3)) * x)) + (a3 |^ 4)) + (((((256 * a3) * (x |^ 3)) - ((192 * (a3 |^ 2)) * (x |^ 2))) + ((48 * (a3 |^ 3)) * x)) - (4 * (a3 |^ 4)))) + ((16 * a2) * (((16 * (x |^ 2)) - ((8 * x) * a3)) + (a3 |^ 2)))) + ((64 * a1) * ((4 * x) - a3))) + (256 * a0)) by A1, A8, A6, A3

      .= (256 * ((((x |^ 4) + ((4 * p) * (x |^ 2))) + ((8 * q) * x)) + (4 * r))) by A9;

      hence thesis;

    end;

    theorem :: POLYEQ_5:22

    

     Th22: a3 = ( - (((s1 + s2) + s3) + s4)) & a2 = ((((((s1 * s2) + (s1 * s3)) + (s1 * s4)) + (s2 * s3)) + (s2 * s4)) + (s3 * s4)) & a1 = ( - (((((s1 * s2) * s3) + ((s1 * s2) * s4)) + ((s1 * s3) * s4)) + ((s2 * s3) * s4))) & a0 = (((s1 * s2) * s3) * s4) implies ((((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff z = s1 or z = s2 or z = s3 or z = s4)

    proof

      assume a3 = ( - (((s1 + s2) + s3) + s4)) & a2 = ((((((s1 * s2) + (s1 * s3)) + (s1 * s4)) + (s2 * s3)) + (s2 * s4)) + (s3 * s4)) & a1 = ( - (((((s1 * s2) * s3) + ((s1 * s2) * s4)) + ((s1 * s3) * s4)) + ((s2 * s3) * s4))) & a0 = (((s1 * s2) * s3) * s4);

      

      then

       A1: ((((z - s1) * (z - s2)) * (z - s3)) * (z - s4)) = (((((((z * z) * z) * z) + (((a3 * z) * z) * z)) + ((a2 * z) * z)) + (a1 * z)) + a0)

      .= (((((z |^ 4) + (a3 * ((z * z) * z))) + ((a2 * z) * z)) + (a1 * z)) + a0) by Th3

      .= (((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z * z))) + (a1 * z)) + a0) by Th2

      .= (((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) by Th1;

      hereby

        assume (((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 ;

        then

         A2: (((z - s1) * (z - s2)) * (z - s3)) = 0 or (z - s4) = 0 by A1;

        assume that

         A3: ( not z = s1) & not z = s2 and

         A4: not z = s3;

        

         A5: (z - s3) <> 0 by A4;

        (z - s1) <> 0 & (z - s2) <> 0 by A3;

        hence z = s4 by A2, A5;

      end;

      assume z = s1 or z = s2 or z = s3 or z = s4;

      hence (((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 by A1;

    end;

    theorem :: POLYEQ_5:23

    

     Th23: q <> 0 & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) implies (((((z |^ 4) + ((4 * p) * (z |^ 2))) + ((8 * q) * z)) + (4 * r)) = 0 iff z = ((s1 + s2) + s3) or z = ((s1 - s2) - s3) or z = ((( - s1) + s2) - s3) or z = ((( - s1) - s2) + s3))

    proof

      set z1 = ((s1 + s2) + s3), z2 = ((s1 - s2) - s3), z3 = ((( - s1) + s2) - s3), z4 = ((( - s1) - s2) + s3);

      assume q <> 0 ;

      then

       A1: (q * q) <> 0 ;

      assume

       A2: s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))));

      assume

       A3: s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))));

      

       A4: (s2 * s2) = (s2 |^ 2) by Th1

      .= ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by A3, Th7;

      

       A5: (s1 * s1) = (s1 |^ 2) by Th1

      .= ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by A2, Th7;

      then

       A6: (((s1 * s1) * (s2 * s2)) * ( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) = ( - ( - (q |^ 2))) by A4, Th19;

      then

       A7: ((s1 * s1) * (s2 * s2)) <> 0 by A1, Th1;

      ((s1 * s2) * (s1 * s2)) <> 0 by A1, A6, Th1;

      then

       A8: (s1 * s2) <> 0 ;

      assume

       A9: s3 = ( - (q / (s1 * s2)));

      

      then

       A10: ( - (((((z1 * z2) * z3) + ((z1 * z2) * z4)) + ((z1 * z3) * z4)) + ((z2 * z3) * z4))) = ( - ((8 * (s1 * s2)) * ( - (q / (s1 * s2)))))

      .= ( - ((8 * (s1 * s2)) * (( - q) / (s1 * s2)))) by XCMPLX_1: 187

      .= ( - (8 * ((s1 * s2) * (( - q) / (s1 * s2)))))

      .= ( - (8 * (( - q) / ((s1 * s2) / (s1 * s2))))) by XCMPLX_1: 81

      .= ( - (8 * (( - q) / 1))) by A8, XCMPLX_1: 60

      .= (8 * q);

      

       A11: (s3 * s3) = ((( - q) / (s1 * s2)) * ( - (q / (s1 * s2)))) by A9, XCMPLX_1: 187

      .= ((( - q) / (s1 * s2)) * (( - q) / (s1 * s2))) by XCMPLX_1: 187

      .= ((( - q) * ( - q)) / ((s1 * s2) * (s1 * s2))) by XCMPLX_1: 76

      .= ((q * q) / ((s1 * s1) * (s2 * s2)))

      .= ((( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) * ((s1 * s1) * (s2 * s2))) / ((s1 * s1) * (s2 * s2))) by A6, Th1

      .= ( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by A7, XCMPLX_1: 89;

      then

       A12: (((s1 * s1) + (s2 * s2)) + (s3 * s3)) = ( - (2 * p)) by A5, A4, Th17;

      then

       A13: ( - (((z1 + z2) + z3) + z4)) = 0 & ((((((z1 * z2) + (z1 * z3)) + (z1 * z4)) + (z2 * z3)) + (z2 * z4)) + (z3 * z4)) = (4 * p);

      (((z1 * z2) * z3) * z4) = (((((s1 * s1) + (s2 * s2)) + (s3 * s3)) * (((s1 * s1) + (s2 * s2)) + (s3 * s3))) - (4 * ((((s1 * s1) * (s2 * s2)) + ((s1 * s1) * (s3 * s3))) + ((s2 * s2) * (s3 * s3)))))

      .= ((( - (2 * p)) * ( - (2 * p))) - (4 * ((((s1 * s1) * (s2 * s2)) + ((s1 * s1) * (s3 * s3))) + ((s2 * s2) * (s3 * s3))))) by A12

      .= ((4 * (p * p)) - (4 * ((p |^ 2) - r))) by A5, A4, A11, Th18

      .= ((4 * (p |^ 2)) - (4 * ((p |^ 2) - r))) by Th1

      .= (4 * r);

      then (((((z |^ 4) + ( 0 * (z |^ 3))) + ((4 * p) * (z |^ 2))) + ((8 * q) * z)) + (4 * r)) = 0 iff z = z1 or z = z2 or z = z3 or z = z4 by A13, A10, Th22;

      hence thesis;

    end;

    theorem :: POLYEQ_5:24

    p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & q <> 0 & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) implies ((((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff z = (((s1 + s2) + s3) - (a3 / 4)) or z = (((s1 - s2) - s3) - (a3 / 4)) or z = (((( - s1) + s2) - s3) - (a3 / 4)) or z = (((( - s1) - s2) + s3) - (a3 / 4)))

    proof

      assume

       A1: p = (((8 * a2) - (3 * (a3 |^ 2))) / 32);

      set x = (z + (a3 / 4));

      assume that

       A2: q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) and

       A3: q <> 0 ;

      assume

       A4: r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024);

      

       A5: z = (x - (a3 / 4));

      assume s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2)));

      then ((((x |^ 4) + ((4 * p) * (x |^ 2))) + ((8 * q) * x)) + (4 * r)) = 0 iff x = ((s1 + s2) + s3) or x = ((s1 - s2) - s3) or x = ((( - s1) + s2) - s3) or x = ((( - s1) - s2) + s3) by A3, Th23;

      hence thesis by A1, A2, A4, A5, Th21;

    end;

    theorem :: POLYEQ_5:25

    p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & q = 0 & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) implies ((((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff z = ((2 -root ( - (2 * (p - s1)))) - (a3 / 4)) or z = (( - (2 -root ( - (2 * (p - s1))))) - (a3 / 4)) or z = ((2 -root ( - (2 * (p + s1)))) - (a3 / 4)) or z = (( - (2 -root ( - (2 * (p + s1))))) - (a3 / 4)))

    proof

      assume

       A1: p = (((8 * a2) - (3 * (a3 |^ 2))) / 32);

      set x = (z + (a3 / 4));

      assume that

       A2: q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) and

       A3: q = 0 ;

      

       A4: z = (x - (a3 / 4));

      assume r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024);

      then

       A5: (((((z |^ 4) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff ((((x |^ 4) + ((4 * p) * (x |^ 2))) + ((8 * q) * x)) + (4 * r)) = 0 by A1, A2, A4, Th21;

      assume

       A6: s1 = (2 -root ((p |^ 2) - r));

      set y = (x |^ 2);

      

       A7: (y |^ 2) = (x |^ (2 * 2)) by NEWTON: 9

      .= (x |^ 4);

      

       A8: (x |^ 2) = (( - (2 * p)) + ((2 -root ( delta ((4 * r),(4 * p),1))) / 2)) iff x = (2 -root (( - (2 * p)) + ((2 -root ( delta ((4 * r),(4 * p),1))) / 2))) or x = ( - (2 -root (( - (2 * p)) + ((2 -root ( delta ((4 * r),(4 * p),1))) / 2)))) by Th10;

      

       A9: (x |^ 2) = (( - (2 * p)) - ((2 -root ( delta ((4 * r),(4 * p),1))) / 2)) iff x = (2 -root (( - (2 * p)) - ((2 -root ( delta ((4 * r),(4 * p),1))) / 2))) or x = ( - (2 -root (( - (2 * p)) - ((2 -root ( delta ((4 * r),(4 * p),1))) / 2)))) by Th10;

      

       A10: (4 |^ 2) = (4 * 4) by Th1

      .= 16;

      (((1 * (y |^ 2)) + ((4 * p) * y)) + (4 * r)) = 0 iff y = (( - ((4 * p) / (2 * 1))) + ((2 -root ( delta ((4 * r),(4 * p),1))) / (2 * 1))) or y = (( - ((4 * p) / (2 * 1))) - ((2 -root ( delta ((4 * r),(4 * p),1))) / (2 * 1))) by Th12;

      then

       A11: (((1 * (y |^ 2)) + ((4 * p) * y)) + (4 * r)) = 0 iff z = ((2 -root (( - (2 * p)) + ((2 -root ( delta ((4 * r),(4 * p),1))) / 2))) - (a3 / 4)) or z = (( - (2 -root (( - (2 * p)) + ((2 -root ( delta ((4 * r),(4 * p),1))) / 2)))) - (a3 / 4)) or z = ((2 -root (( - (2 * p)) - ((2 -root ( delta ((4 * r),(4 * p),1))) / 2))) - (a3 / 4)) or z = (( - (2 -root (( - (2 * p)) - ((2 -root ( delta ((4 * r),(4 * p),1))) / 2)))) - (a3 / 4)) by A8, A9;

      (2 -root 16) = (2 -real-root 16) by Th8

      .= (2 -Root 16) by POWER:def 1

      .= 4 by A10, PREPOWER:def 2;

      

      then ((2 -root ( delta ((4 * r),(4 * p),1))) / 4) = (2 -root ((16 * ((p * p) - r)) / 16)) by Th9

      .= s1 by A6, Th1;

      hence thesis by A3, A5, A7, A11;

    end;

    definition

      let a0,a1,a2,a3 be Complex;

      :: POLYEQ_5:def5

      func 1_root_of_quartic (a0,a1,a2,a3) -> Complex means

      : Def5: ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & it = ((2 -root ( - (2 * (p - s1)))) - (a3 / 4)) if (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0

      otherwise ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & it = (((s1 + s2) + s3) - (a3 / 4));

      existence

      proof

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s3 = ( - (q / (s1 * s2))), IT = (((s1 + s2) + s3) - (a3 / 4));

        thus (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 implies ex IT,p,r,s1 be Complex st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & IT = ((2 -root ( - (2 * (p - s1)))) - (a3 / 4))

        proof

          set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ((p |^ 2) - r)), IT = ((2 -root ( - (2 * (p - s1)))) - (a3 / 4));

          assume (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 ;

          take IT, p, r, s1;

          thus thesis;

        end;

        assume (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) <> 0 ;

        take IT, p, q, r, s1, s2, s3;

        thus thesis;

      end;

      uniqueness ;

      correctness ;

      :: POLYEQ_5:def6

      func 2_root_of_quartic (a0,a1,a2,a3) -> Complex means

      : Def6: ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & it = (( - (2 -root ( - (2 * (p - s1))))) - (a3 / 4)) if (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0

      otherwise ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & it = (((( - s1) - s2) + s3) - (a3 / 4));

      existence

      proof

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s3 = ( - (q / (s1 * s2))), IT = (((( - s1) - s2) + s3) - (a3 / 4));

        thus (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 implies ex IT,p,r,s1 be Complex st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & IT = (( - (2 -root ( - (2 * (p - s1))))) - (a3 / 4))

        proof

          set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ((p |^ 2) - r)), IT = (( - (2 -root ( - (2 * (p - s1))))) - (a3 / 4));

          assume (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 ;

          take IT, p, r, s1;

          thus thesis;

        end;

        assume (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) <> 0 ;

        take IT, p, q, r, s1, s2, s3;

        thus thesis;

      end;

      uniqueness ;

      correctness ;

      :: POLYEQ_5:def7

      func 3_root_of_quartic (a0,a1,a2,a3) -> Complex means

      : Def7: ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & it = ((2 -root ( - (2 * (p + s1)))) - (a3 / 4)) if (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0

      otherwise ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & it = (((( - s1) + s2) - s3) - (a3 / 4));

      existence

      proof

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s3 = ( - (q / (s1 * s2))), IT = (((( - s1) + s2) - s3) - (a3 / 4));

        thus (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 implies ex IT,p,r,s1 be Complex st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & IT = ((2 -root ( - (2 * (p + s1)))) - (a3 / 4))

        proof

          set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ((p |^ 2) - r)), IT = ((2 -root ( - (2 * (p + s1)))) - (a3 / 4));

          assume (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 ;

          take IT, p, r, s1;

          thus thesis;

        end;

        assume (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) <> 0 ;

        take IT, p, q, r, s1, s2, s3;

        thus thesis;

      end;

      uniqueness ;

      correctness ;

      :: POLYEQ_5:def8

      func 4_root_of_quartic (a0,a1,a2,a3) -> Complex means

      : Def8: ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & it = (( - (2 -root ( - (2 * (p + s1))))) - (a3 / 4)) if (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0

      otherwise ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & it = (((s1 - s2) - s3) - (a3 / 4));

      existence

      proof

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s3 = ( - (q / (s1 * s2))), IT = (((s1 - s2) - s3) - (a3 / 4));

        thus (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 implies ex IT,p,r,s1 be Complex st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & IT = (( - (2 -root ( - (2 * (p + s1))))) - (a3 / 4))

        proof

          set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ((p |^ 2) - r)), IT = (( - (2 -root ( - (2 * (p + s1))))) - (a3 / 4));

          assume (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 ;

          take IT, p, r, s1;

          thus thesis;

        end;

        assume (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) <> 0 ;

        take IT, p, q, r, s1, s2, s3;

        thus thesis;

      end;

      uniqueness ;

      correctness ;

    end

    theorem :: POLYEQ_5:26

    

     Th26: (((( 1_root_of_quartic (a0,a1,a2,a3)) + ( 2_root_of_quartic (a0,a1,a2,a3))) + ( 3_root_of_quartic (a0,a1,a2,a3))) + ( 4_root_of_quartic (a0,a1,a2,a3))) = ( - a3)

    proof

      per cases ;

        suppose

         A1: (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 ;

        then

         A2: (ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 3_root_of_quartic (a0,a1,a2,a3)) = ((2 -root ( - (2 * (p + s1)))) - (a3 / 4))) & ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 4_root_of_quartic (a0,a1,a2,a3)) = (( - (2 -root ( - (2 * (p + s1))))) - (a3 / 4)) by Def7, Def8;

        (ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 1_root_of_quartic (a0,a1,a2,a3)) = ((2 -root ( - (2 * (p - s1)))) - (a3 / 4))) & ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 2_root_of_quartic (a0,a1,a2,a3)) = (( - (2 -root ( - (2 * (p - s1))))) - (a3 / 4)) by A1, Def5, Def6;

        hence thesis by A2;

      end;

        suppose

         A3: (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) <> 0 ;

        then

         A4: (ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 3_root_of_quartic (a0,a1,a2,a3)) = (((( - s1) + s2) - s3) - (a3 / 4))) & ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 4_root_of_quartic (a0,a1,a2,a3)) = (((s1 - s2) - s3) - (a3 / 4)) by Def7, Def8;

        (ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 1_root_of_quartic (a0,a1,a2,a3)) = (((s1 + s2) + s3) - (a3 / 4))) & ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 2_root_of_quartic (a0,a1,a2,a3)) = (((( - s1) - s2) + s3) - (a3 / 4)) by A3, Def5, Def6;

        hence thesis by A4;

      end;

    end;

    theorem :: POLYEQ_5:27

    

     Th27: ((((((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) + (( 1_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3)))) + (( 1_root_of_quartic (a0,a1,a2,a3)) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + (( 2_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3)))) + (( 2_root_of_quartic (a0,a1,a2,a3)) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + (( 3_root_of_quartic (a0,a1,a2,a3)) * ( 4_root_of_quartic (a0,a1,a2,a3)))) = a2

    proof

      per cases ;

        suppose

         A1: (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 ;

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ((p |^ 2) - r));

        set t1 = (2 -root ( - (2 * (p - s1)))), t2 = (2 -root ( - (2 * (p + s1))));

        

         A2: (ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 3_root_of_quartic (a0,a1,a2,a3)) = ((2 -root ( - (2 * (p + s1)))) - (a3 / 4))) & ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 4_root_of_quartic (a0,a1,a2,a3)) = (( - (2 -root ( - (2 * (p + s1))))) - (a3 / 4)) by A1, Def7, Def8;

        (ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 1_root_of_quartic (a0,a1,a2,a3)) = ((2 -root ( - (2 * (p - s1)))) - (a3 / 4))) & ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 2_root_of_quartic (a0,a1,a2,a3)) = (( - (2 -root ( - (2 * (p - s1))))) - (a3 / 4)) by A1, Def5, Def6;

        

        hence ((((((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) + (( 1_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3)))) + (( 1_root_of_quartic (a0,a1,a2,a3)) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + (( 2_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3)))) + (( 2_root_of_quartic (a0,a1,a2,a3)) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + (( 3_root_of_quartic (a0,a1,a2,a3)) * ( 4_root_of_quartic (a0,a1,a2,a3)))) = (((((((4 + 1) + 1) * a3) * a3) / 16) - (t1 * t1)) - (t2 * t2)) by A2

        .= (((((3 * a3) * a3) / 8) - (t1 |^ 2)) - (t2 * t2)) by Th1

        .= (((((3 * a3) * a3) / 8) - ( - (2 * (p - s1)))) - (t2 * t2)) by Th7

        .= (((((3 * a3) * a3) / 8) + (2 * (p - s1))) - (t2 |^ 2)) by Th1

        .= (((((3 * a3) * a3) / 8) + (2 * (p - s1))) - ( - (2 * (p + s1)))) by Th7

        .= ((((3 * a3) * a3) / 8) + (((8 * a2) - (3 * (a3 |^ 2))) / 8))

        .= ((((3 * a3) * a3) / 8) + (((8 * a2) - (3 * (a3 * a3))) / 8)) by Th1

        .= a2;

      end;

        suppose

         A3: (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) <> 0 ;

        then

         A4: (ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 3_root_of_quartic (a0,a1,a2,a3)) = (((( - s1) + s2) - s3) - (a3 / 4))) & ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 4_root_of_quartic (a0,a1,a2,a3)) = (((s1 - s2) - s3) - (a3 / 4)) by Def7, Def8;

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s3 = ( - (q / (s1 * s2)));

        

         A5: (s2 * s2) = (s2 |^ 2) by Th1

        .= ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by Th7;

        

         A6: (s1 * s1) = (s1 |^ 2) by Th1

        .= ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by Th7;

        then

         A7: (((s1 * s1) * (s2 * s2)) * ( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) = ( - ( - (q |^ 2))) by A5, Th19;

        (q * q) <> 0 by A3;

        then

         A8: ((s1 * s1) * (s2 * s2)) <> 0 by A7, Th1;

        

         A9: (s3 * s3) = ((( - q) / (s1 * s2)) * ( - (q / (s1 * s2)))) by XCMPLX_1: 187

        .= ((( - q) / (s1 * s2)) * (( - q) / (s1 * s2))) by XCMPLX_1: 187

        .= ((( - q) * ( - q)) / ((s1 * s2) * (s1 * s2))) by XCMPLX_1: 76

        .= ((q * q) / ((s1 * s1) * (s2 * s2)))

        .= ((( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) * ((s1 * s1) * (s2 * s2))) / ((s1 * s1) * (s2 * s2))) by A7, Th1

        .= ( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by A8, XCMPLX_1: 89;

        (ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 1_root_of_quartic (a0,a1,a2,a3)) = (((s1 + s2) + s3) - (a3 / 4))) & ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 2_root_of_quartic (a0,a1,a2,a3)) = (((( - s1) - s2) + s3) - (a3 / 4)) by A3, Def5, Def6;

        

        hence ((((((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) + (( 1_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3)))) + (( 1_root_of_quartic (a0,a1,a2,a3)) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + (( 2_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3)))) + (( 2_root_of_quartic (a0,a1,a2,a3)) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + (( 3_root_of_quartic (a0,a1,a2,a3)) * ( 4_root_of_quartic (a0,a1,a2,a3)))) = (( - (2 * (((s1 * s1) + (s2 * s2)) + (s3 * s3)))) + (((3 * a3) * a3) / 8)) by A4

        .= (( - (2 * ( - (2 * p)))) + (((3 * a3) * a3) / 8)) by A6, A5, A9, Th17

        .= (((4 * ((8 * a2) - (3 * (a3 |^ 2)))) / 32) + (((3 * a3) * a3) / 8))

        .= (((4 * ((8 * a2) - (3 * (a3 * a3)))) / 32) + (((3 * a3) * a3) / 8)) by Th1

        .= a2;

      end;

    end;

    theorem :: POLYEQ_5:28

    

     Th28: (((((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) * ( 3_root_of_quartic (a0,a1,a2,a3))) + ((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + ((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + ((( 2_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3)))) = ( - a1)

    proof

      per cases ;

        suppose

         A1: (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 ;

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ((p |^ 2) - r));

        set t1 = (2 -root ( - (2 * (p - s1)))), t2 = (2 -root ( - (2 * (p + s1))));

        

         A2: (ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 3_root_of_quartic (a0,a1,a2,a3)) = ((2 -root ( - (2 * (p + s1)))) - (a3 / 4))) & ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 4_root_of_quartic (a0,a1,a2,a3)) = (( - (2 -root ( - (2 * (p + s1))))) - (a3 / 4)) by A1, Def7, Def8;

        (ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 1_root_of_quartic (a0,a1,a2,a3)) = ((2 -root ( - (2 * (p - s1)))) - (a3 / 4))) & ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 2_root_of_quartic (a0,a1,a2,a3)) = (( - (2 -root ( - (2 * (p - s1))))) - (a3 / 4)) by A1, Def5, Def6;

        

        hence (((((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) * ( 3_root_of_quartic (a0,a1,a2,a3))) + ((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + ((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + ((( 2_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3)))) = (((( - (t1 * t1)) + ((a3 * a3) / 16)) * ( - (a3 / 2))) + ((( - (t2 * t2)) + ((a3 * a3) / 16)) * ( - (a3 / 2)))) by A2

        .= (((( - (t1 |^ 2)) + ((a3 * a3) / 16)) * ( - (a3 / 2))) + ((( - (t2 * t2)) + ((a3 * a3) / 16)) * ( - (a3 / 2)))) by Th1

        .= (((( - (t1 |^ 2)) + ((a3 * a3) / 16)) * ( - (a3 / 2))) + ((( - (t2 |^ 2)) + ((a3 * a3) / 16)) * ( - (a3 / 2)))) by Th1

        .= (((( - ( - (2 * (p - s1)))) + ((a3 * a3) / 16)) * ( - (a3 / 2))) + ((( - (t2 |^ 2)) + ((a3 * a3) / 16)) * ( - (a3 / 2)))) by Th7

        .= (((( - ( - (2 * (p - s1)))) + ((a3 * a3) / 16)) * ( - (a3 / 2))) + ((( - ( - (2 * (p + s1)))) + ((a3 * a3) / 16)) * ( - (a3 / 2)))) by Th7

        .= (((a2 - ((3 * (a3 |^ 2)) / 8)) + ((a3 * a3) / 8)) * ( - (a3 / 2)))

        .= (((a2 - ((3 * (a3 * a3)) / 8)) + ((a3 * a3) / 8)) * ( - (a3 / 2))) by Th1

        .= ((((a3 * a3) * a3) / 8) - ((a2 * a3) / 2))

        .= (((a3 |^ 3) / 8) - (((4 * a2) * a3) / 8)) by Th2

        .= ( - a1) by A1;

      end;

        suppose

         A3: (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) <> 0 ;

        then

         A4: (ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 3_root_of_quartic (a0,a1,a2,a3)) = (((( - s1) + s2) - s3) - (a3 / 4))) & ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 4_root_of_quartic (a0,a1,a2,a3)) = (((s1 - s2) - s3) - (a3 / 4)) by Def7, Def8;

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s3 = ( - (q / (s1 * s2)));

        

         A5: (s2 * s2) = (s2 |^ 2) by Th1

        .= ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by Th7;

        

         A6: (s1 * s1) = (s1 |^ 2) by Th1

        .= ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by Th7;

        then

         A7: (((s1 * s1) * (s2 * s2)) * ( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) = ( - ( - (q |^ 2))) by A5, Th19;

        

         A8: (q * q) <> 0 by A3;

        then

         A9: ((s1 * s1) * (s2 * s2)) <> 0 by A7, Th1;

        ((s1 * s2) * (s1 * s2)) <> 0 by A8, A7, Th1;

        then

         A10: (s1 * s2) <> 0 ;

        

         A11: (s3 * s3) = ((( - q) / (s1 * s2)) * ( - (q / (s1 * s2)))) by XCMPLX_1: 187

        .= ((( - q) / (s1 * s2)) * (( - q) / (s1 * s2))) by XCMPLX_1: 187

        .= ((( - q) * ( - q)) / ((s1 * s2) * (s1 * s2))) by XCMPLX_1: 76

        .= ((q * q) / ((s1 * s1) * (s2 * s2)))

        .= ((( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) * ((s1 * s1) * (s2 * s2))) / ((s1 * s1) * (s2 * s2))) by A7, Th1

        .= ( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by A9, XCMPLX_1: 89;

        (ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 1_root_of_quartic (a0,a1,a2,a3)) = (((s1 + s2) + s3) - (a3 / 4))) & ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 2_root_of_quartic (a0,a1,a2,a3)) = (((( - s1) - s2) + s3) - (a3 / 4)) by A3, Def5, Def6;

        

        hence (((((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) * ( 3_root_of_quartic (a0,a1,a2,a3))) + ((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + ((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3)))) + ((( 2_root_of_quartic (a0,a1,a2,a3)) * ( 3_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3)))) = ((((((s1 * s1) + (s2 * s2)) + (s3 * s3)) * a3) - (((a3 * a3) * a3) / 16)) + (((8 * s1) * s2) * s3)) by A4

        .= (((( - (2 * p)) * a3) - (((a3 * a3) * a3) / 16)) + (((8 * s1) * s2) * ( - (q / (s1 * s2))))) by A6, A5, A11, Th17

        .= (((( - (((16 * a2) / 32) * a3)) + (((6 * (a3 |^ 2)) / 32) * a3)) - (((a3 * a3) * a3) / 16)) - (((8 * s1) * s2) * (q / (s1 * s2))))

        .= (((( - ((a2 / 2) * a3)) + (((6 * (a3 * a3)) / 32) * a3)) - (((a3 * a3) * a3) / 16)) - (((8 * s1) * s2) * (q / (s1 * s2)))) by Th1

        .= ((( - ((a2 * a3) / 2)) + ((((2 * a3) * a3) * a3) / 16)) - (8 * ((s1 * s2) * (q / (s1 * s2)))))

        .= ((( - ((a2 * a3) / 2)) + ((((2 * a3) * a3) * a3) / 16)) - (8 * (q / ((s1 * s2) / (s1 * s2))))) by XCMPLX_1: 81

        .= ((( - ((a2 * a3) / 2)) + ((((2 * a3) * a3) * a3) / 16)) - (8 * (q / 1))) by A10, XCMPLX_1: 60

        .= ((( - a1) + ((((2 * a3) * a3) * a3) / 16)) - ((8 * (a3 |^ 3)) / 64))

        .= ((( - a1) + ((((2 * a3) * a3) * a3) / 16)) - ((8 * ((a3 * a3) * a3)) / 64)) by Th2

        .= ( - a1);

      end;

    end;

    theorem :: POLYEQ_5:29

    

     Th29: (((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) * ( 3_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3))) = a0

    proof

      per cases ;

        suppose

         A1: (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) = 0 ;

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ((p |^ 2) - r));

        set t1 = (2 -root ( - (2 * (p - s1)))), t2 = (2 -root ( - (2 * (p + s1))));

        

         A2: (ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 3_root_of_quartic (a0,a1,a2,a3)) = ((2 -root ( - (2 * (p + s1)))) - (a3 / 4))) & ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 4_root_of_quartic (a0,a1,a2,a3)) = (( - (2 -root ( - (2 * (p + s1))))) - (a3 / 4)) by A1, Def7, Def8;

        (ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 1_root_of_quartic (a0,a1,a2,a3)) = ((2 -root ( - (2 * (p - s1)))) - (a3 / 4))) & ex p, r, s1 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ((p |^ 2) - r)) & ( 2_root_of_quartic (a0,a1,a2,a3)) = (( - (2 -root ( - (2 * (p - s1))))) - (a3 / 4)) by A1, Def5, Def6;

        

        hence (((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) * ( 3_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3))) = ((( - (t1 * t1)) + ((a3 * a3) / 16)) * (( - (t2 * t2)) + ((a3 * a3) / 16))) by A2

        .= ((( - (t1 |^ 2)) + ((a3 * a3) / 16)) * (( - (t2 * t2)) + ((a3 * a3) / 16))) by Th1

        .= ((( - (t1 |^ 2)) + ((a3 * a3) / 16)) * (( - (t2 |^ 2)) + ((a3 * a3) / 16))) by Th1

        .= ((( - ( - (2 * (p - s1)))) + ((a3 * a3) / 16)) * (( - (t2 |^ 2)) + ((a3 * a3) / 16))) by Th7

        .= ((( - ( - (2 * (p - s1)))) + ((a3 * a3) / 16)) * (( - ( - (2 * (p + s1)))) + ((a3 * a3) / 16))) by Th7

        .= (((((4 * p) * p) + (((((2 * 2) * p) * a3) * a3) / 16)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) - (4 * (s1 * s1)))

        .= (((((4 * p) * p) + ((((4 * p) * a3) * a3) / 16)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) - (4 * (s1 |^ 2))) by Th1

        .= ((((4 * (p * p)) + ((((4 * p) * a3) * a3) / 16)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) - (4 * ((p |^ 2) - r))) by Th7

        .= ((((4 * (p |^ 2)) + ((((4 * p) * a3) * a3) / 16)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) - (4 * ((p |^ 2) - r))) by Th1

        .= (((((p * a3) * a3) / 4) + ((((a3 * a3) * (a3 * a3)) / 16) / 16)) + (4 * r))

        .= (((((p * a3) * a3) / 4) + ((((a3 * a3) * (a3 |^ 2)) / 16) / 16)) + (4 * r)) by Th1

        .= (((((p * a3) * a3) / 4) + (((a3 * a3) * (a3 |^ 2)) / 256)) + (((a0 - ((a3 * a1) / 4)) + (((a3 |^ 2) * a2) / 16)) - ((3 * (a3 |^ 4)) / 256)))

        .= (((((p * a3) * a3) / 4) + (((a3 * a3) * (a3 |^ 2)) / 256)) + (((a0 - ((a3 * a1) / 4)) + (((a3 |^ 2) * a2) / 16)) - ((3 * (((a3 * a3) * a3) * a3)) / 256))) by Th3

        .= (((((p * a3) * a3) / 4) + (((a3 * a3) * (a3 |^ 2)) / 256)) + (((a0 - ((a3 * a1) / 4)) + (((a3 |^ 2) * a2) / 16)) - ((((3 * a3) * a3) * (a3 * a3)) / 256)))

        .= (((((p * a3) * a3) / 4) + (((a3 * a3) * (a3 |^ 2)) / 256)) + (((a0 - ((a3 * a1) / 4)) + (((a3 |^ 2) * a2) / 16)) - ((((3 * a3) * a3) * (a3 |^ 2)) / 256))) by Th1

        .= ((((a0 + ((a2 * (a3 * a3)) / 16)) - ((((4 * (a3 |^ 2)) * a3) * a3) / 128)) - ((a3 * a1) / 4)) + (((a3 |^ 2) * a2) / 16))

        .= ((((a0 + ((a2 * (a3 |^ 2)) / 16)) - ((((a3 |^ 2) * a3) * a3) / 32)) - ((a3 * a1) / 4)) + (((a3 |^ 2) * a2) / 16)) by Th1

        .= (((a0 + (((2 * a2) * (a3 |^ 2)) / 16)) - ((((a3 |^ 2) * a3) * a3) / 32)) - ((a3 * a1) / 4))

        .= (((a0 + (((2 * a2) * (a3 * a3)) / 16)) - ((((a3 |^ 2) * a3) * a3) / 32)) - ((a3 * a1) / 4)) by Th1

        .= (((a0 + ((((4 * a2) * a3) * a3) / 32)) - ((((a3 * a3) * a3) * a3) / 32)) - (((8 * a3) * a1) / 32)) by Th1

        .= (a0 + ((((((4 * a2) * a3) - ((a3 * a3) * a3)) - (8 * a1)) * a3) / 32))

        .= (a0 + ((((((4 * a2) * a3) - (a3 |^ 3)) - (8 * a1)) * a3) / 32)) by Th2

        .= a0 by A1;

      end;

        suppose

         A3: (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) <> 0 ;

        then

         A4: (ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 3_root_of_quartic (a0,a1,a2,a3)) = (((( - s1) + s2) - s3) - (a3 / 4))) & ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 4_root_of_quartic (a0,a1,a2,a3)) = (((s1 - s2) - s3) - (a3 / 4)) by Def7, Def8;

        set p = (((8 * a2) - (3 * (a3 |^ 2))) / 32), q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64), r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024), s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))), s3 = ( - (q / (s1 * s2)));

        

         A5: (s2 * s2) = (s2 |^ 2) by Th1

        .= ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by Th7;

        set r1 = (s1 * s1), r2 = (s2 * s2), r3 = (s3 * s3);

        

         A6: (s1 * s1) = (s1 |^ 2) by Th1

        .= ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by Th7;

        then

         A7: (((s1 * s1) * (s2 * s2)) * ( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) = ( - ( - (q |^ 2))) by A5, Th19;

        

         A8: (q * q) <> 0 by A3;

        then ((s1 * s2) * (s1 * s2)) <> 0 by A7, Th1;

        then

         A9: (s1 * s2) <> 0 ;

        

         A10: ((s1 * s1) * (s2 * s2)) <> 0 by A8, A7, Th1;

        

         A11: (s3 * s3) = ((( - q) / (s1 * s2)) * ( - (q / (s1 * s2)))) by XCMPLX_1: 187

        .= ((( - q) / (s1 * s2)) * (( - q) / (s1 * s2))) by XCMPLX_1: 187

        .= ((( - q) * ( - q)) / ((s1 * s2) * (s1 * s2))) by XCMPLX_1: 76

        .= ((q * q) / ((s1 * s1) * (s2 * s2)))

        .= ((( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) * ((s1 * s1) * (s2 * s2))) / ((s1 * s1) * (s2 * s2))) by A7, Th1

        .= ( 3_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p))) by A10, XCMPLX_1: 89;

        then

         A12: ((r1 + r2) + r3) = ( - (2 * p)) by A6, A5, Th17;

        (ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 1_root_of_quartic (a0,a1,a2,a3)) = (((s1 + s2) + s3) - (a3 / 4))) & ex p, q, r, s1, s2, s3 st p = (((8 * a2) - (3 * (a3 |^ 2))) / 32) & q = ((((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3)) / 64) & r = (((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4))) / 1024) & s1 = (2 -root ( 1_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s2 = (2 -root ( 2_root_of_cubic (( - (q |^ 2)),((p |^ 2) - r),(2 * p)))) & s3 = ( - (q / (s1 * s2))) & ( 2_root_of_quartic (a0,a1,a2,a3)) = (((( - s1) - s2) + s3) - (a3 / 4)) by A3, Def5, Def6;

        

        hence (((( 1_root_of_quartic (a0,a1,a2,a3)) * ( 2_root_of_quartic (a0,a1,a2,a3))) * ( 3_root_of_quartic (a0,a1,a2,a3))) * ( 4_root_of_quartic (a0,a1,a2,a3))) = (((((((r1 + r2) + r3) * ((r1 + r2) + r3)) - (4 * (((r1 * r2) + (r1 * r3)) + (r2 * r3)))) - (((((r1 + r2) + r3) * a3) * a3) / 8)) - ((((2 * s1) * s2) * s3) * a3)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) by A4

        .= (((((( - (2 * p)) * ( - (2 * p))) - (4 * ((p |^ 2) - r))) - (((( - (2 * p)) * a3) * a3) / 8)) - ((((2 * s1) * s2) * s3) * a3)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) by A6, A5, A11, A12, Th18

        .= ((((((4 * p) * p) - (4 * ((p |^ 2) - r))) + ((((2 * p) * a3) * a3) / 8)) - ((((2 * s1) * s2) * s3) * a3)) + (((((a3 * a3) * a3) * a3) / 16) / 16))

        .= ((((((4 * p) * p) - (4 * ((p * p) - r))) + ((((2 * p) * a3) * a3) / 8)) - ((((2 * s1) * s2) * s3) * a3)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) by Th1

        .= ((((4 * r) + ((((2 * p) * a3) * a3) / 8)) + ((2 * a3) * ((s1 * s2) * (q / (s1 * s2))))) + (((((a3 * a3) * a3) * a3) / 16) / 16))

        .= ((((4 * r) + ((((2 * p) * a3) * a3) / 8)) + ((2 * a3) * (q / ((s1 * s2) / (s1 * s2))))) + (((((a3 * a3) * a3) * a3) / 16) / 16)) by XCMPLX_1: 81

        .= ((((4 * r) + ((((2 * p) * a3) * a3) / 8)) + ((2 * a3) * (q / 1))) + (((((a3 * a3) * a3) * a3) / 16) / 16)) by A9, XCMPLX_1: 60

        .= (((((4 * ((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 |^ 2)) * a2)) - (3 * (a3 |^ 4)))) / 1024) + ((((((8 * a2) - (3 * (a3 |^ 2))) / 32) * a3) * a3) / 4)) + (((2 * a3) * (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3))) / 64)) + (((((a3 * a3) * a3) * a3) / 16) / 16))

        .= (((((4 * ((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 * a3)) * a2)) - (3 * (a3 |^ 4)))) / 1024) + ((((((8 * a2) - (3 * (a3 |^ 2))) / 32) * a3) * a3) / 4)) + (((2 * a3) * (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3))) / 64)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) by Th1

        .= (((((4 * ((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 * a3)) * a2)) - (3 * (a3 |^ 4)))) / 1024) + ((((((8 * a2) - (3 * (a3 * a3))) / 32) * a3) * a3) / 4)) + (((2 * a3) * (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3))) / 64)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) by Th1

        .= (((((4 * ((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 * a3)) * a2)) - (3 * (((a3 * a3) * a3) * a3)))) / 1024) + ((((((8 * a2) - (3 * (a3 * a3))) / 32) * a3) * a3) / 4)) + (((2 * a3) * (((8 * a1) - ((4 * a2) * a3)) + (a3 |^ 3))) / 64)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) by Th3

        .= (((((4 * ((((256 * a0) - ((64 * a3) * a1)) + ((16 * (a3 * a3)) * a2)) - (3 * (((a3 * a3) * a3) * a3)))) / 1024) + ((((((8 * a2) - (3 * (a3 * a3))) / 32) * a3) * a3) / 4)) + (((2 * a3) * (((8 * a1) - ((4 * a2) * a3)) + ((a3 * a3) * a3))) / 64)) + (((((a3 * a3) * a3) * a3) / 16) / 16)) by Th2

        .= a0;

      end;

    end;

    ::$Notion-Name

    theorem :: POLYEQ_5:30

    a4 <> 0 implies ((((((a4 * (z |^ 4)) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 iff z = ( 1_root_of_quartic ((a0 / a4),(a1 / a4),(a2 / a4),(a3 / a4))) or z = ( 2_root_of_quartic ((a0 / a4),(a1 / a4),(a2 / a4),(a3 / a4))) or z = ( 3_root_of_quartic ((a0 / a4),(a1 / a4),(a2 / a4),(a3 / a4))) or z = ( 4_root_of_quartic ((a0 / a4),(a1 / a4),(a2 / a4),(a3 / a4))))

    proof

      assume

       A1: a4 <> 0 ;

      set s4 = ( 4_root_of_quartic ((a0 / a4),(a1 / a4),(a2 / a4),(a3 / a4)));

      set s3 = ( 3_root_of_quartic ((a0 / a4),(a1 / a4),(a2 / a4),(a3 / a4)));

      set s2 = ( 2_root_of_quartic ((a0 / a4),(a1 / a4),(a2 / a4),(a3 / a4)));

      set s1 = ( 1_root_of_quartic ((a0 / a4),(a1 / a4),(a2 / a4),(a3 / a4)));

      ( - (a3 / a4)) = (((s1 + s2) + s3) + s4) by Th26;

      then

       A2: (a3 / a4) = ( - (((s1 + s2) + s3) + s4));

      ( - (a1 / a4)) = (((((s1 * s2) * s3) + ((s1 * s2) * s4)) + ((s1 * s3) * s4)) + ((s2 * s3) * s4)) by Th28;

      then

       A3: (a1 / a4) = ( - (((((s1 * s2) * s3) + ((s1 * s2) * s4)) + ((s1 * s3) * s4)) + ((s2 * s3) * s4)));

      ((((((z |^ 4) + ((a3 / a4) * (z |^ 3))) + ((a2 / a4) * (z |^ 2))) + ((a1 / a4) * z)) + (a0 / a4)) * a4) = (((((a4 * (z |^ 4)) + (((a3 / a4) * a4) * (z |^ 3))) + (((a2 / a4) * a4) * (z |^ 2))) + (((a1 / a4) * a4) * z)) + ((a0 / a4) * a4))

      .= (((((a4 * (z |^ 4)) + (((a3 / a4) * a4) * (z |^ 3))) + (((a2 / a4) * a4) * (z |^ 2))) + (((a1 / a4) * a4) * z)) + a0) by A1, XCMPLX_1: 87

      .= (((((a4 * (z |^ 4)) + (((a3 / a4) * a4) * (z |^ 3))) + (((a2 / a4) * a4) * (z |^ 2))) + (a1 * z)) + a0) by A1, XCMPLX_1: 87

      .= (((((a4 * (z |^ 4)) + (((a3 / a4) * a4) * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) by A1, XCMPLX_1: 87

      .= (((((a4 * (z |^ 4)) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) by A1, XCMPLX_1: 87;

      then

       A4: (((((z |^ 4) + ((a3 / a4) * (z |^ 3))) + ((a2 / a4) * (z |^ 2))) + ((a1 / a4) * z)) + (a0 / a4)) = 0 iff (((((a4 * (z |^ 4)) + (a3 * (z |^ 3))) + (a2 * (z |^ 2))) + (a1 * z)) + a0) = 0 by A1;

      (a2 / a4) = ((((((s1 * s2) + (s1 * s3)) + (s1 * s4)) + (s2 * s3)) + (s2 * s4)) + (s3 * s4)) & (a0 / a4) = (((s1 * s2) * s3) * s4) by Th27, Th29;

      hence thesis by A4, A2, A3, Th22;

    end;