Metamath Proof Explorer


Theorem bnj1441

Description: First-order logic and set theory. (Contributed by Jonathan Ben-Naim, 3-Jun-2011) Add disjoint variable condition to avoid ax-13 . See bnj1441g for a less restrictive version requiring more axioms. (Revised by Gino Giotto, 20-Jan-2024) (New usage is discouraged.)

Ref Expression
Hypotheses bnj1441.1
|- ( x e. A -> A. y x e. A )
bnj1441.2
|- ( ph -> A. y ph )
Assertion bnj1441
|- ( z e. { x e. A | ph } -> A. y z e. { x e. A | ph } )

Proof

Step Hyp Ref Expression
1 bnj1441.1
 |-  ( x e. A -> A. y x e. A )
2 bnj1441.2
 |-  ( ph -> A. y ph )
3 df-rab
 |-  { x e. A | ph } = { x | ( x e. A /\ ph ) }
4 1 2 hban
 |-  ( ( x e. A /\ ph ) -> A. y ( x e. A /\ ph ) )
5 4 hbab
 |-  ( z e. { x | ( x e. A /\ ph ) } -> A. y z e. { x | ( x e. A /\ ph ) } )
6 3 5 hbxfreq
 |-  ( z e. { x e. A | ph } -> A. y z e. { x e. A | ph } )