Question

Factorise the trinomial $x^2-x-12$.

• A. $(x-4)(x+3)$
• B. $(x+4)(x+3)$
• C. $(x+4)(x-3)$
• D. $(x-4)(x-3)$

Answer 1

The correct option is A $(x-4)(x+3)$

Given trinomial = $x^2-x-12$
Product of the first and the last term
= $-12\times x^2$ = $-12x^2$
Now we have to split the middle term in such a way that their product is $-12x^2$ and sum is $-x$. The two terms are $-4x$ and $3x$ .
So,
$x^2-x-12$ $=x^2-4x+3x-12=x(x-4)+3(x-4)=(x-4)(x+3)$

Therefore, $x^2-x-12=(x-4)(x+3)$