Question

Which function below results in f(2) = 13? *

f(x) = x² + 8
f(x) = 3x² + 1
f(x) = 2x³ + 5
f(x) = x² + x

Answer 1

f(x) = 3x² + 1

Explanation:

In this question, we need to find what equations equals to 13 when we plug in 2 to x.

Solve the equations to find which one is true:

f(2) = 2² + 8

= 4 + 8

= 12

---------------

f(2) = 3(2)² + 1

= 3(4) + 1

= 12 + 1

= 13

---------------

f(2) = 2(2)³ + 5

= 2(8) + 5

= 16 + 5

= 21

---------------

f(2) = 2² + 2

= 4 + 2

= 6

You will see that the 2nd equation, f(x) = 3x² + 1, is the only one that equals to 13, which makes it correct.