Which of these functions is not a linear function? A. f(x) = x
B. f(x) = 3^x
C. f(x) = 3x
D. f(x) = 3x - 2

This problem has to do with the relative "strengths" of functions. I'd recommend you try plugging in x values for each of the equations to see how the behaviors differ.

For example:

x = 1:
f(1) = 3
g(1) = 3
h(1) = 2
x = 10:
f(10) = 30
g(10) = 300
h(10) = 1024
x = 100:
f(100) = 300
g(100) = 30,000
h(100) = 1.27 x 10^30
What do these answers tell you about the behaviors of the three different equations.