reserve a, a9, a1, a2, a3, b, b9, c, c9, d, d9, h, p, q, x, x1, x2, x3, u, v,
  y, z for Real;

theorem
  for a, b, x being Complex holds a <> 0 & Polynom(a,b,x) = 0
  implies x = -(b/a)
proof
  let a, b, x be Complex;
  assume that
A1: a <> 0 and
A2: Polynom(a,b,x) = 0;
  a"*(-b) = a"*(a*x) by A2
    .= (a"*a)*x;
  then 1*x = a"*(-b) by A1,XCMPLX_0:def 7;
  then x = -(a"*b);
  hence thesis by XCMPLX_0:def 9;
end;
