proposition: Lemma Rplus_lt_reg_r (x y z : R) : y + x < z + x -> y < z.
proof: Proof. first [ intro H ; apply Rplus_lt_reg_r with x ; now rewrite 2!(Rplus_comm x) | exact: Rplus_lt_reg_r ]. Qed.
imports: Coq(Reals Psatz ssreflect) Coq(ssrbool) mathcomp(seq)