theorem
  t*z divides (t-z)|^(2*n+1) - (t|^(2*n+1) - z|^(2*n+1))
  proof
    A1: (-z)|^(2*n+1) = -z|^(2*n+1) by POWER:2;
    t*z divides (t-z)|^(2*n+1) - (t|^(2*n+1) + (-z)|^(2*n+1)) by Th19;
    hence thesis by A1;
  end;
