Theorem eliminable2b

Description: A theorem used to prove the base case of the Eliminability Theorem (see section comment). (Contributed by BJ, 19-Oct-2019) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	eliminable2b	|- ( { x | ph } = y <-> A. z ( z e. { x | ph } <-> z e. y ) )

Proof

Step	Hyp	Ref	Expression
1		dfcleq	|- ( { x | ph } = y <-> A. z ( z e. { x | ph } <-> z e. y ) )