proposition: Lemma mulrz_suml : forall n I r (P : pred I) (F : I -> M), (\sum_(i <- r | P i) F i) *~ n= \sum_(i <- r | P i) F i *~ n.
proof: Proof. by rewrite -/M^z; apply: scaler_sumr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)