(** ** Question 3 *)
(* 10:49 *)
(** 3.a. *)

(* Specifications: *)
Lemma Q3a : forall n, v n = 2 * (2/3) ^ n.
(** 3.b. *)
Lemma Q3b : forall n, u n = 2 * (2/3)^n + INR n.
Lemma Q3c : is_lim_seq u p_infty.
Definition Su (n : nat) : R := sum_f_R0 u n.