Question

For what values of x is the rational expression below undefined?

Check all that apply.
x+8
——
x *squared* -2x-24
A. -8
B. 6
C. 8
D. -4
E. -6
F. 4

Answer 1

B and D

Explanation:

Given

`(x+8)/(x^2-2x-24)`

The denominator of the rational function cannot be zero as this would make it undefined. Equating the denominator to zero and solving gives the values that x cannot be.

Solve x² - 2x - 24 = 0, that is

(x - 6)(x + 4) = 0

Equate each factor to zero and solve for x

x - 6 = 0 ⇒ x = 6 → B

x + 4 = 0 ⇒ x = - 4 → D