One of the factors of x² -
x – 6 is how do i work this out on paper?

Could you re-write that for me?
I'm not sure I'm understanding it right.

X^2 -x- 6 equals (x-3)(x+2). Just look at the negative six and think, what two numbers give me this? Then, get a pair of what you find, and see if the two numbers added equal to negative one (which comes from the negative "x" as the coefficient is always 1). That's how you get -3 and +2.