Theorem wl-nfalv 36901

Description: If 𝑥 is not present in 𝜑, it is not free in ∀𝑦𝜑. (Contributed by Wolf Lammen, 11-Jan-2020.)

Assertion

Ref	Expression
wl-nfalv	⊢ Ⅎ𝑥∀𝑦𝜑

Distinct variable group:   𝜑,𝑥

Allowed substitution hint:   𝜑(𝑦)

Proof of Theorem wl-nfalv

Step	Hyp	Ref	Expression
1		ax-5 1905	. . 3 ⊢ (𝜑 → ∀𝑥𝜑)
2	1	hbal 2159	. 2 ⊢ (∀𝑦𝜑 → ∀𝑥∀𝑦𝜑)
3	2	nf5i 2134	1 ⊢ Ⅎ𝑥∀𝑦𝜑

Syntax hints:  ∀wal 1531  Ⅎwnf 1777

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1789  ax-4 1803  ax-5 1905  ax-10 2129  ax-11 2146

This theorem depends on definitions:  df-bi 206  df-ex 1774  df-nf 1778

This theorem is referenced by: (None)