proposition: Lemma pexpr_eq1 x n : (0 < n)%N -> 0 <= x -> (x ^+ n == 1) = (x == 1).
proof: Proof. by move=> ngt0 xge0; rewrite !eq_le expr_le1 // expr_ge1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)