reserve a,b,c,d,a9,b9,c9,d9,y,x1,u,v for Real,
  s,t,h,z,z1,z2,z3,s1,s2,s3 for Complex;

theorem Th16:
  z1 <> 0 & Polynom(z1,z2,z) = 0 implies z = -(z2/z1)
proof
  assume z1 <> 0 & Polynom(z1,z2,z) = 0;
  then z = (-z2)*z1" by XCMPLX_1:203;
  hence thesis;
end;
