Metamath Proof Explorer


Theorem nfiu1OLD

Description: Obsolete version of nfiu1 as of 14-May-2025. (Contributed by NM, 12-Oct-2003) (Proof modification is discouraged.) (New usage is discouraged.)

Ref Expression
Assertion nfiu1OLD
|- F/_ x U_ x e. A B

Proof

Step Hyp Ref Expression
1 df-iun
 |-  U_ x e. A B = { y | E. x e. A y e. B }
2 nfre1
 |-  F/ x E. x e. A y e. B
3 2 nfab
 |-  F/_ x { y | E. x e. A y e. B }
4 1 3 nfcxfr
 |-  F/_ x U_ x e. A B