Question

If one of the factors of $x^2+x-20$ is $(x+5)$, find the other factor.

• A. $x–5$
• B. $x+2$
• C. $x+4$
• D. $x–4$

Answer 1

The correct option is D $x–4$

Let $p\left(x\right)=x^2+x-20$
$p\left(x\right)=x^2+5x-4x-20$
$p\left(x\right)=x(x+5)-4(x+5)$
$p\left(x\right)=(x-4)(x+5)$
$(x-4)$ is also a factor of $x^2+x-20$.