What I mean by the complete way is this example:

x^2 - 12x + x - 12

x^2 - 12x + x - 12

x (x - 12) - 1(x - 12)

(x - 12) (x + 1)

x^2 - x + 12x - 12

x^2 + 11x - 12

These are the problems that I'm stuck on:

1. 5x^2 - 80

2. x^2 - 100

3. x^3 - 3x^2 + 4x

4. 81x^2 - 1

5. x^2 + 13x - 30