Question

If (x - 5) is a factor of f(x), which of the following must be true?

O A root of f(x) is x = -5.
O A root of f(x) is x = 5.
O Both x = -5 and x = 5 are rots of f(x).
O Neither x = -5 nor x = 5 is a root of f(x).

Answer 1

The second choice is true.

Answer 2

A root of f(x) is x=5

Explanation:

If (x-5) is a factor of f(x), then 5 is a root.

If (x+5) is a factor of f(x), then -5 is a root.

So we are only given that (x-5) is a factor of f(x), so we only know that x=5 is a root.

This is by factor theorem. It says if (x-c) is a factor then f(c)=0 which means c is a root of f(x) because it makes the expressions equal to 0.