please answer both questions

Complete the following proof, which proves the statement by contradiction: If a is even, then 4a2. proof. Let a be and 4a2 By the definition of for some integer k. It follows that a2= =4( Since is an integer, must be an integer. Since a2 equals times an integer, This contradicts with that 4a2. Hence, the assumption that a is even and 4a2 false. Hint: To prove the following statement by contradiction: If a is even, then 4a2. What would be assumed to be true? 4a2 4a2 a is odd a is even a is even and 4a2 a is even and 4a2 a is odd and 4a2 a is odd and 4a2 Prove the following statement by contrapositive. For any integer n, if n2+3n+5 is even, then n is odd