Question

For what values of x is the rational expression below undefined? x-7/x^2-7x-8

check all that apply
a. 1
b. 7
c. 8
d. -8
e. -7
f. -1

Answer 1

we have

f(x)=(x-7)/(x²-7x-8)

resolving the quadratic equation
using a graph tool-------- > see the attached figure
x=-1 x=8
therefore
(x-7)/(x²-7x-8)=(x-7)/[(x+1)*(x-8)

the answer is -1 and 8