unfold quo.
generalize (quo_dec a b H);intro;elim s;trivial.
Qed.

(* Specifications: *)
(** if b | a then (n*a/b) = n*(a/b) *)
Lemma quo_mult : forall (a b:nat)(H:divides a b),forall (n:nat),(b<>O)->(quo (a*n) b (divides_mult b a n H))=n*(quo a b H).
intros.