proposition: Lemma sumrMnl I r P (F : I -> V) n : \sum_(i <- r | P i) F i *+ n = (\sum_(i <- r | P i) F i) *+ n.
proof: Proof. by rewrite (big_morph _ (mulrnDl n) (mul0rn _)). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)