Admitted.  QuickChick plus_id_exercise.

(* Specifications: *)
Theorem mult_0_plus : forall n m : nat,
(0 + n) * m = n * m. Admitted. (* QuickChick mult_0_plus. *)
Theorem mult_S_1 : forall n m : nat,
m = S n ->
m * (1 + n) = m * m.