proposition: Lemma eqrXz2 n x y : n != 0 -> 0 <= x -> 0 <= y -> (x ^ n == y ^ n) = (x == y).
proof: Proof. by move=> *; rewrite (inj_in_eq (pexpIrz _)). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)