Theorem eliminable2a

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	eliminable2a	|- ( x = { y | ph } <-> A. z ( z e. x <-> z e. { y | ph } ) )

Proof

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