theorem Th18:
  for a be FinSequence of K st len a = len b2 & g is additive homogeneous holds
  g.Sum(lmlt(a,b2)) = Sum(lmlt(a,g*b2))
proof
  let a be FinSequence of K such that
A1: len a = len b2 and
A2: g is additive homogeneous;
  thus g.Sum(lmlt(a,b2)) = Sum(g*lmlt(a,b2)) by A2,Th16
    .= Sum(lmlt(a,g*b2)) by A1,A2,Th17;
end;
