Question

On the function machine shown below, the function rule is given as a variable expression. When the output is 99, what is the input? *

a 20

b 9

c 100

d 10

Answer 1

Answer: option d.

Explanation:

We have the function:

y = f(x) = x^2 - 1

The output is 99 when y = 99, and the input is x.

Then we need to solve:

y = 99 = x^2 - 1

for x.

99 = x^2 - 1

99 + 1 =x^2

100 = x^2

√100 = x

10 = x

The correct option is d, input equals 10.