proposition: Lemma mulrzAr n x y : x * (y *~ n) = (x * y) *~ n.
proof: Proof. by elim: n=> //= *; rewrite ?mulr0 ?mulr0z // /intmul /= -mulrnAr -?mulrN. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)