reserve p, q, x, y for Real,
  n for Nat;

theorem
  for f being real-valued FinSequence holds x * (-f) = - (x*f)
proof
  let f be real-valued FinSequence;
  thus x * (-f) = x*((-1)*f) .= (-1) * x*f by RVSUM_1:49
    .= - x*f by RVSUM_1:49;
end;
