Question

Which of the following sentences is/are valid?
∃x ∃ y P(x,y) ≡ ∃ y ∃ x P(y,x)
∀x ∃ y P(x,y) ≡ ∃ y ∀ x P(x,y)
∀x ∃ y P(x,y) ⊃ ∃ y ∀ x P(x,y)
∃y ∀ x P(x,y) ⊃ ∀ x ∃ y P(x,y)

Answer 1

srry.. don't know about it

Answer 2

pls ask question properly...