proposition: Lemma expfB m n x : n < m -> x ^+ (m - n) = x ^+ m / x ^+ n.
proof: Proof. by move=> lt_n_m; apply: expfB_cond; case: eqP => // _; apply: ltnW. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)