Metamath Proof Explorer

Theorem 2exbii

Description: Inference adding two existential quantifiers to both sides of an equivalence. (Contributed by NM, 16-Mar-1995)

Ref Expression
Hypothesis 2exbii.1 φ ψ
Assertion 2exbii x y φ x y ψ


Step Hyp Ref Expression
1 2exbii.1 φ ψ
2 1 exbii y φ y ψ
3 2 exbii x y φ x y ψ