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