Question

Factorise
$x^2-x-156$

Answer 1

We have:

$x^2-x-156$

We have to split (-1) into two numbers such that their sum is ( -1) and their product is (-156).

Clearly, $-13+12=-1$ and $-13\times 12=-156$.

$\therefore x^2-x-156=x^2-13x+12x-156=x(x-13)+12(x-13)=(x-13)(x+12)$