Theorem nfoprab2

Description: The abstraction variables in an operation class abstraction are not free. (Contributed by NM, 25-Apr-1995) (Revised by David Abernethy, 30-Jul-2012)

	Ref	Expression
Assertion	nfoprab2	|- F/_ y { <. <. x , y >. , z >. | ph }

Proof

Step	Hyp	Ref	Expression
1		df-oprab	|- { <. <. x , y >. , z >. | ph } = { w | E. x E. y E. z ( w = <. <. x , y >. , z >. /\ ph ) }
2		nfe1	|- F/ y E. y E. z ( w = <. <. x , y >. , z >. /\ ph )
3	2	nfex	|- F/ y E. x E. y E. z ( w = <. <. x , y >. , z >. /\ ph )
4	3	nfab	|- F/_ y { w | E. x E. y E. z ( w = <. <. x , y >. , z >. /\ ph ) }
5	1 4	nfcxfr	|- F/_ y { <. <. x , y >. , z >. | ph }