Factoring with the difference of squares

I think factoring is something which becomes internal, you see a problem, make a guess, and then check. The best method is trial and error till it becomes intuitive.

Still the difference of squares method is often taught, and so I will show it here.

Basically the difference of squares is always factored in the following form:

(x+y)(x-y)

Which equals (x² - y²)

Example

x² - 9

9 is a perfect square so we can use the memorized formula

(x-3)(x+3)

Again, I prefer gaining an intuitive understanding of factoring, but memorizing a rule like this can help till you gain an intuitive understanding.