The first function is linear and the second is neither.
A linear function has a constant rate of change.
The rate of change is the slope; it is found using the formula
Between the first two points, the slope is

Between the next two points, the slope is

This function has a constant slope, so the function is linear.
In order for a function to be exponential, the percent change between y-values must be the same.
To find the percent of change, we use the formula
For the first two points, this is
(5-2)/2 = 3/2 = 1.5
For the next two points, this is
(9-5)/5 = 4/5 = 0.8
This is not the same; this means it is not an exponential function.
Question: Drag and drop the answer into the box to identify each function as linear, exponential, or neither.
x 1 3 5
f(x) 11 31 51
x 0 2 4
f(x) 2 5 9