Question

If f(3) = 15 and f(5) = 45, which of the following could be f(x)?

a. 4x + 3
b. 2x² – 2x
c. 2x² - x
d. 2x² - 5
e. 5x²

Answer 1

f(x) = 2x² - x
f(3) = 2(3)² - 3
f(3) = 2(9) - 3
f(3) = 18 - 3
f(3) = 15

f(x) = 2x² - x
f(5) = 2(5)² - 5
f(5) = 2(25) - 5
f(5) = 50 - 5
f(5) = 45

The answer is C.