theorem Th17:
    for f be Polynomial of 0,R holds f is Constant
    proof
      let f be Polynomial of 0,R;
      assume not f is Constant; then
      consider b being bag of 0 such that
A2:   b <> EmptyBag 0 & f.b <> 0.R by POLYNOM7:def 7;
      b = EmptyBag 0;
      hence contradiction by A2;
    end;
