Direct Proofs

Prove the following via a Direct Proof:

1.1

The square of an even natural number is even.

1.2

The square of an odd natural number is odd.

1.3

If n is a positive integer, then the quantity n 2 + 3n + 2 is even.

1.4

The sum of two odd natural numbers is even.

1.5

Prove that the sum of an even integer and an odd integer is odd.