proposition: Lemma mediant_1 : forall m n m' n' : Z, (m' * n < m * n')%Z -> ((m + m') * n < m * (n + n'))%Z.
proof: Proof. intros. rewrite Zmult_plus_distr_r. rewrite Zmult_plus_distr_l. apply Zplus_lt_compat_l. assumption. Qed.
imports: Coq(Lia)