How to prove there is no natural deduction proof for $$\forall x(P(x)\lor Q(x))\vdash\forall xP(x) \lor ∀xQ(x).$$
I don't know how to prove this, maybe by semantic?
2026-03-28 17:04:56.1774717496
How to prove there is no natural deduction proof for $\forall x(P(x)\lor Q(x))\vdash\forall xP(x) \lor ∀xQ(x).$
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