Question

Which function is (x-1) a real root?

Answer 1

Answer:

D

Step-by-step explanation:

According to the Factor Theorem:

In order for a factor in the form of $(x-a)$ to be a root for a function $f(x)$, $f(a)$ must be 0.

Our factor is $(x-1)$.

Therefore, $a=1$.

So, we will evaluate $f(1)$ for all the choices.

Doing so, we can see that, starting from the top, we have:

$\begin{aligned}f_1(1)&=-12\\ f_2(1) &=8 \\ f_3(1)&=24 \\ f_4(1)&=0 \end{aligned}$

The choice that yields 0 as an answer is D.

So, the function for which $(x-1)$ is a real root is choice D.