proposition: Lemma nmulrn_rge0 x n : x < 0 -> 0 <= x *+ n = (n == 0)%N.
proof: Proof. by move=> x_lt0; rewrite -(mulr0n x) ler_nMn2l ?leqn0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)