I am part of the logic club at my school and the question of the week was;
Use formal deduction for predicate calculus to show that the following argument is valid. State each rule you use.
Premise 1: ∀x(F(x) → G(x)) → ∃x(H(x) ∧ ¬I(x))
Premise 2: ∀x(H(x) → I(x))
Can anybody help me out? I know I have to use the 11 rules. For the first one I've never seen something with two -->'s before in a row