proposition: Lemma mulrN1z x : x *~ (- 1) = - x.
proof: Proof. by rewrite -scalezrE scaleN1r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)