proposition: Lemma zdiv_plus_compat : forall a b c : Z, ZDivides a b -> ZDivides a c -> ZDivides a (b + c).
proof: Proof. intros. elim H. intro x. intros. elim H0. intro y. intros. split with (x + y)%Z. rewrite H1. rewrite H2. symmetry in |- *. rewrite (Zmult_comm a). rewrite (Zmult_comm a). rewrite (Zmult_comm a). apply Zmult_plus_distr_l. Qed.
imports: ZArith Wf_nat lemmas natZ dec exp