Theorem nfeqf1

An equation between setvar is free of any other setvar. Usage of this theorem is discouraged because it depends on [ax-13]. (Contributed by Wolf Lammen, 10-Jun-2019.) (New usage is discouraged.)

Conclusion
\( \vdash \neg \forall x \, x = y' \rightarrow \Finv x \, y' = z' \)
Proof
l0
nfeqf2
\( \vdash \neg \forall x \, x = y' \rightarrow \Finv x \, z' = y' \)
equcom
nfbii _
\( \vdash \Finv x \, z' = y' \leftrightarrow \Finv x \, y' = z' \)
sylib l0 _