proposition: Lemma mulRN1 x : x * - 1 == - x.
proof: Proof. by rewrite mulRN mulR1. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div order) mathcomp(ssralg ssrnum ssrint rat intdiv) Coq(Morphisms Setoid) fourcolor(real realsyntax)