I'm new to natural deduction and is having trouble proofing these formulas, any help or hint is appreciated.
$$ \neg \exists p(x)\rightarrow \forall x \neg p(x)\\ \exists x \neg p(x) \rightarrow \neg \forall xp(x) $$
I'm new to natural deduction and is having trouble proofing these formulas, any help or hint is appreciated.
$$ \neg \exists p(x)\rightarrow \forall x \neg p(x)\\ \exists x \neg p(x) \rightarrow \neg \forall xp(x) $$
Hint
1) $¬∃p(x)$ --- premise
2) $p(x)$ --- assumed [a]
3) $∃p(x)$ --- from 2) by $∃$-intro
4) $\bot$ --- from 1) and 3)
5) $¬p(x)$ --- from 2) and 5) $¬$-intro, discharging [a]
Thus, from 1) and 6) we have :
the result follows by $\to$-intro.