Metamath Proof Explorer


Theorem bnj213

Description: First-order logic and set theory. (Contributed by Jonathan Ben-Naim, 3-Jun-2011) (New usage is discouraged.)

Ref Expression
Assertion bnj213 predXARA

Proof

Step Hyp Ref Expression
1 df-bnj14 predXAR=yA|yRX
2 1 ssrab3 predXARA