proposition: Lemma mulrzAl n x y : (x *~ n) * y = (x * y) *~ n.
proof: Proof. by elim: n=> //= *; rewrite ?mul0r ?mulr0z // /intmul /= -mulrnAl -?mulNr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)