Definition Qmult_resp_Qlt_pos_l:= Qlt_Qmult_cancel_l: forall t x y : Q, Zero < t -> t * x < t * y -> x < y.

Lemma Qmult_Qlt_Qle_nonneg_pos_compat: forall n m p q, n < p -> m <= q -> Zero <= n -> Zero < q -> n * m < p * q.