proposition: Lemma exprz_gt0 n x (hx : 0 < x) : (0 < x ^ n).
proof: Proof. by case: n=> n; rewrite ?NegzE -?invr_expz ?invr_gt0 ?exprn_gt0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)