Factoring polynomials...

I need to factor these polynomials but I don't quite understand them.

a^2+2ab+b^2-c^2

4-a^2-2ab-b^2

x^4-(4x-5)^2

It would be great if someone could show me the steps.

1. (a+b-c)(a+b+c)

2. -(a+b-2)(a+b+2)

3. (x-1) (x+5) (x^2-4x+5)

10 points!