theorem Th17:
  for x being Real holds |(x*p1, p2)| = x*|(p1, p2)|
proof
  let x be Real;
  reconsider f1=p1,f2=p2 as FinSequence of REAL by EUCLID:24;
  reconsider q1 = p1 as Element of REAL n by EUCLID:22;
  len f1=n & len f2=n by CARD_1:def 7;
  hence thesis by RVSUM_1:121;
end;
