proposition: Lemma ratAdd_add_same_l : forall r1 r2 r3, r2 + r1 == r2 + r3 -> r1 == r3.
proof: Proof. intuition. eapply ratAdd_add_same_r. eapply eqRat_trans. apply ratAdd_comm. rewrite H. apply ratAdd_comm. Qed.
imports: micromega.Lia List FCF.StdNat Arith Lia Setoid RelationClasses Coq.Classes.Morphisms