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| Mirrors > Home > ILE Home > Th. List > nfv | GIF version | ||
| Description: If 𝑥 is not present in 𝜑, then 𝑥 is not free in 𝜑. (Contributed by Mario Carneiro, 11-Aug-2016.) | 
| Ref | Expression | 
|---|---|
| nfv | ⊢ Ⅎ𝑥𝜑 | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | ax-17 1540 | . 2 ⊢ (𝜑 → ∀𝑥𝜑) | |
| 2 | 1 | nfi 1476 | 1 ⊢ Ⅎ𝑥𝜑 | 
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