proposition: Lemma Frobenius_autB_comm x y : comm x y -> (x - y)^f = x^f - y^f.
proof: Proof. by move/commrN/Frobenius_autD_comm->; rewrite Frobenius_autN. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)