(** ** Questions 2 *)
(* 8:38 *)
(** 2.a. *)

Lemma RInt_f : is_RInt f ( / exp 1) 1 1.
Fixpoint u (n : nat) : R :=
match n with
| O => 2
| S n => 2/3 * u n + 1/3 * (INR n) + 1
end.