proposition: Lemma ler_wnMn2l x : x <= 0 -> {homo (@GRing.natmul R x) : m n / (n <= m)%N >-> m <= n}.
proof: Proof. by move=> xle0 m n hmn /=; rewrite -lerN2 -!mulNrn ler_wpMn2l // oppr_cp0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)