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Theorem nfxfrOLD 1825
Description: Obsolete proof of nfxfr 1771 as of 6-Oct-2021. (Contributed by Mario Carneiro, 11-Aug-2016.) (Proof modification is discouraged.) (New usage is discouraged.)
Hypotheses
Ref Expression
nfbiiOLD.1 (𝜑𝜓)
nfxfrOLD.2 𝑥𝜓
Assertion
Ref Expression
nfxfrOLD 𝑥𝜑

Proof of Theorem nfxfrOLD
StepHypRef Expression
1 nfxfrOLD.2 . 2 𝑥𝜓
2 nfbiiOLD.1 . . 3 (𝜑𝜓)
32nfbiiOLD 1824 . 2 (Ⅎ𝑥𝜑 ↔ Ⅎ𝑥𝜓)
41, 3mpbir 220 1 𝑥𝜑
Colors of variables: wff setvar class
Syntax hints:  wb 195  wnfOLD 1700
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728
This theorem depends on definitions:  df-bi 196  df-nfOLD 1712
This theorem is referenced by:  nfnf1OLDOLD  2196  nfnanOLD  2226  nf3anOLD  2227  nforOLD  2232  nf3orOLD  2233
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