Factoring help?

Question

Factor each expression as a difference of two squares.
1) a² - (x + 1)²
2) 16 - (2x + y)²
3) x² + 10x + 25 - y²

Answer 1

If you have a^2 - b^2

Then the factored form is (a+b)(a-b)

The third one can be written as: (x+5)^2 - y^2

So a=x+5
and b=y

((x+5)+y)((x+5)-y)

Answer 2

http://www.bacsoftware.co.uk/algebra/downl2.htm