Metamath Proof Explorer


Theorem bj-exalbial

Description: Adding a second quantifier is a tranparent operation, ( E. A. case). (Contributed by BJ, 20-Oct-2019)

Ref Expression
Assertion bj-exalbial x x φ x φ

Proof

Step Hyp Ref Expression
1 nfa1 x x φ
2 1 19.9 x x φ x φ