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