Question

Find the illegal values of b in the fraction.

Answer 1

Denominator can't be zero, so:

b^2 - 2b - 8 = 0
b^2 - 4b + 2b - 8 = 0
b(b-4) + 2(b-4) = 0
(b-4) (b+2) = 0

b-4 = 0
b = 4

b+2 = 0
b = -2

b can't be equal to 4 and -2

Answer: D