proposition: Fact convex_neq a b x y : a < b -> a*x+b*y = a*y+b*x -> x = y.
proof: Proof. intros H. replace b with (a+(b-a)) by lia. apply convex_3; lia. Qed.
imports: List Arith Lia  Undecidability.Shared.Libs.DLW(utils_tac utils_list sums pos vec) Undecidability.H10.Dio(dio_logic dio_elem)