proposition: Lemma ler_nMn2l x : x < 0 -> {mono (@GRing.natmul R x) : m n / (n <= m)%N >-> m <= n}.
proof: Proof. by move=> xlt0 m n /=; rewrite -lerN2 -!mulNrn ler_pMn2l// oppr_gt0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)