proposition: Lemma mulrzBl x y n : (x - y) *~ n = x *~ n - y *~ n.
proof: Proof. by rewrite -scalezrE scalerBr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)