proposition: Lemma ratSubtract_ratAdd_inverse : forall r1 r2, ratSubtract (r1 + r2) r1 == r2.
proof: Proof. intuition. unfold ratSubtract. rattac. Qed.
imports: micromega.Lia List FCF.StdNat Arith Lia Setoid RelationClasses Coq.Classes.Morphisms