proposition: Lemma Qplus_le_r (z x y : Q): z + x <= z + y <-> x <= y.
proof: Proof. do 2 rewrite (Qplus_comm z). apply Qplus_le_l. Qed.
imports: Coq.QArith.QArith Coq.ZArith.ZArith Coq.NArith.NArith Coq.QArith.Qpower Coq.QArith.Qround Coq.QArith.Qround Coq.QArith.Qabs CoRN.stdlib_omissions.List