The Factor Theorem

Hi, I'm having some problems with the Factor Theorem, I use the long division method, but then after that I can't get the other two factors (I don't want to use the quadratic equation -b + or - the square root of b^2 - 4ac divided by 2), I want to use another way, it is supposed to be much simpler, but I never learnt it. Please help a.s.a.p, this work has to be in by tomorrow.

Edit: - Just figured it out within 2 minutes of making this topic, however I'd still like a technical explanation please.