Description: The setvar x is not free in A. x e. A ph . (Contributed by NM, 18-Oct-1996) (Revised by Mario Carneiro, 7-Oct-2016)
Ref | Expression | ||
---|---|---|---|
Assertion | nfra1 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-ral | |
|
2 | nfa1 | |
|
3 | 1 2 | nfxfr | |