Metamath Proof Explorer


Theorem rexcom

Description: Commutation of restricted existential quantifiers. (Contributed by NM, 19-Nov-1995) (Revised by Mario Carneiro, 14-Oct-2016) (Proof shortened by BJ, 26-Aug-2023) (Proof shortened by Wolf Lammen, 8-Dec-2024)

Ref Expression
Assertion rexcom xAyBφyBxAφ

Proof

Step Hyp Ref Expression
1 ralcom xAyB¬φyBxA¬φ
2 ralnex2 xAyB¬φ¬xAyBφ
3 ralnex2 yBxA¬φ¬yBxAφ
4 1 2 3 3bitr3i ¬xAyBφ¬yBxAφ
5 4 con4bii xAyBφyBxAφ