Which one of the following well-formed formulae in predicate calculus is NOT valid? , Which one of the following well-formed formulae in predicate calculus is NOT valid?

Solution

D. ∀x ( p(x) ∨ q(x)) ⇒ (∀x p(x) ∨ ∀x q(x))

Explanation

For every x , p or q is true. It can not imply that Either for every x, p is true OR for every x, q is true. So last option is wrong.