Let A and I be ideals of a KK-algebra X with I ⊆ A. If I is a q-deal of X, then so is A.
Proof. Let I is a q-deal of a KK-algebra X and set s = (x∗0)∗y ∈ A. Since (x∗ 0) ∗ (s ∗y) = s ∗((x ∗ 0) ∗y) = 0 ∈ I. By 3.5(2), we get that x∗ (s ∗y) ∈ I. And since I is a q−ideal, then s ∗ (x ∗ y) ∈ I. Thus s ∗ (x ∗ y) ∈ A and A is an ideal, so x ∗ y ∈ A. Therefore A is a q-ideal.
Corollary 3.7. If zero ideal {0} of KK-algebra X is a q-ideal, then every ideal of X is a q-ideal.