This is a pretty easy method... But, it only works when you can factor something.  As I told you before, except for in math books, things usually don't factor.

But, this is a good method to help you understand what's going on... so, here we go!

We're going to be using one basic idea for these:

If a * b = 0 then a = 0 or b = 0

Think about it!  Let's go back to 2nd grade.

Waaaaaay back...

Fill in the boxes:

4 * ? = 0

? * 5 = 0

a * ? = 0

? * b = 0