proposition: Lemma ltr_nMn2l x : x < 0 -> {mono (@GRing.natmul R x) : m n / (n < m)%N >-> m < n}.
proof: Proof. by move=> x_lt0; apply: leW_nmono (ler_nMn2l _). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)