How do you factor the expression #x^2 + x - 12#?
You look to see if you spot the appropriate factors strait away. If you can not immediately determine them you have to consider all of the potential ones and reason out which ones work.
So for this question:
This is a product so one of the factors is negative and the other positive.
So the difference between the factors of 12 must be 1.
The only factors that give us this difference is 3 and 4.
which is where we started from so these are the factors