# Math Help - Factorising a Polynomial

1. ## Factorising a Polynomial

Hello there,

I've been asked to factorise the following expression:
$x^3 - x^2 - 4x + 2$

From what I can tell, using the factor theorem (if f(a) = 0, then (x - a) is a factor of f(x)) and factors of 2 as input to the function, it can't be factorised. Am I right, can it not be factorised? When I'm asked a question like this, should I simply say "cannot be factorised"?

I'm not asking for answers, because this is for an assignment and I don't want to cheat, I'd just like to know whether I've come to the right conclusion or not.

2. ## Re: Factorising a Polynomial

You can't find an $a$ by inspection wherefore $f(a)=0$, so to solve this equation you need a numerical method. So I would say it can be factorised exactly.