I am completely shit at Maths, pretty please could someone tell me how you're supposed to work out the following so I can hopefully get a C?

1. Factorise fully (n²-a²)-(n-a)²
2. Rearrange the formula to make a the subject: P=n²+a divided by n+a
3. Explain why (n²-a²)-(n-a)² is always an even integer.
4. 8/8 (square root) can be written in the form 8^k. Find the value of k.