Metamath Proof Explorer

Theorem nfnae

Description: All variables are effectively bound in a distinct variable specifier. Usage of this theorem is discouraged because it depends on ax-13 . Use the weaker nfnaew when possible. (Contributed by Mario Carneiro, 11-Aug-2016) (New usage is discouraged.)

Ref Expression
Assertion nfnae z ¬ x x = y


Step Hyp Ref Expression
1 nfae z x x = y
2 1 nfn z ¬ x x = y