proposition: Lemma expr_ge1 n x : (0 < n)%N -> 0 <= x -> (1 <= x ^+ n) = (1 <= x).
proof: Proof. by move=> ngt0 xge0; rewrite -{1}[1](expr1n _ n) ler_pXn2r // [_ \in _]ler01. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)