proposition: Lemma ler_nM2l x : x < 0 -> {mono *%R x : x y /~ x <= y}.
proof: Proof. by move=> x_lt0 y z /=; rewrite -lerN2 -!mulNr ler_pM2l ?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)