proposition: Lemma exprz_ge0 n x (hx : 0 <= x) : (0 <= x ^ n).
proof: Proof. by case: n=> n; rewrite ?NegzE -?invr_expz ?invr_ge0 ?exprn_ge0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)