Lemma Qquadratic_sg_denom_nonzero_Zero_always_Zero_always : forall (k f h : Z) (p1 p2 : Qpositive), k <> 0%Z -> (0 < f)%Z -> (0 < h)%Z -> Qquadratic_sg_denom_nonzero 0 (k * f) 0 (k * h) p1 p2.