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Theorem nfs1 2528
Description: If 𝑦 is not free in 𝜑, 𝑥 is not free in [𝑦 / 𝑥]𝜑. Usage of this theorem is discouraged because it depends on ax-13 2391. Check out nfs1v 2161 for a version requiring less axioms. (Contributed by Mario Carneiro, 11-Aug-2016.) (New usage is discouraged.)
Hypothesis
Ref Expression
nfs1.1 𝑦𝜑
Assertion
Ref Expression
nfs1 𝑥[𝑦 / 𝑥]𝜑

Proof of Theorem nfs1
StepHypRef Expression
1 nfs1.1 . . . 4 𝑦𝜑
21nf5ri 2196 . . 3 (𝜑 → ∀𝑦𝜑)
32hbsb3 2527 . 2 ([𝑦 / 𝑥]𝜑 → ∀𝑥[𝑦 / 𝑥]𝜑)
43nf5i 2151 1 𝑥[𝑦 / 𝑥]𝜑
Colors of variables: wff setvar class
Syntax hints:  wnf 1785  [wsb 2070
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1971  ax-7 2016  ax-10 2146  ax-12 2178  ax-13 2391
This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-ex 1782  df-nf 1786  df-sb 2071
This theorem is referenced by:  sb8  2560  sb8e  2561
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