proposition: Lemma mult_wdr : forall x y1 y2 : R, y1 [=] y2 -> x[*]y1 [=] x[*]y2.
proof: Proof. intros; algebra. Qed.
imports: CoRN.tactics.CornTac CoRN.algebra.CSums CoRN.algebra.CAbMonoids Coq.Sorting.Permutation CoRN.util.SetoidPermutation Coq.Setoids.Setoid Coq.Classes.Morphisms Coq(Lia)