Metamath Proof Explorer


Theorem wl-ax11-lem7

Description: Lemma. (Contributed by Wolf Lammen, 30-Jun-2019)

Ref Expression
Assertion wl-ax11-lem7 x ¬ x x = y φ ¬ x x = y x φ

Proof

Step Hyp Ref Expression
1 nfna1 x ¬ x x = y
2 1 19.28 x ¬ x x = y φ ¬ x x = y x φ