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