proposition: Lemma pmulrz_rlt0 x n (x0 : 0 < x) : x *~ n < 0 = (n < 0).
proof: Proof. by rewrite -(mulr0z x) ltr_pMz2l. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)