proposition: Lemma ltr_nM2l x : x < 0 -> {mono *%R x : x y /~ x < y}.
proof: Proof. by move=> x_lt0; apply: leW_nmono (ler_nM2l _). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)