Theorem sbequ6

Description: Substitution does not change a distinctor. Usage of this theorem is discouraged because it depends on ax-13 . (Contributed by NM, 5-Aug-1993) (New usage is discouraged.)

	Ref	Expression
Assertion	sbequ6	$$⊢\left[w/z\right]\neg \forall xx=y\leftrightarrow \neg \forall xx=y$$

Proof

Step	Hyp	Ref	Expression
1		nfnae	$$⊢Ⅎz\neg \forall xx=y$$
2	1	sbf	$$⊢\left[w/z\right]\neg \forall xx=y\leftrightarrow \neg \forall xx=y$$