Question

Determine the factors of x2 − 12x − 20.

(x − 2)(x + 10)

(x − 10)(x + 2)

(x − 5)(x + 4)

Prime

Answer 1

We want `factors` of -20 that will `add` to give us -12.

\[\large -5 \cdot 4=-20\]But when we try to add these,\[\large -5+4=-1 \qquad \qquad -1\ne-12\]Hmm so those factors don't work.


\[\large -10\cdot2=-20\]Let's try adding them.\[\large -10+2=-8\qquad\qquad -8\ne-12\]

You could also try \(-2\cdot10\) but you would still run into the same problem.
This appears to be prime.
Hopefully this helps you understand why.

Answer 2

Thank youuu! It did help (: