Answer: It is a nonlinear function.
Explanation:
A function is said to be linear if the rate of change of dependent varaible (y) with respect to independent variable (x) is constant.
Rate of change in function

The table gives the speeds recorded by the speedometer on Sully's car with respect to time. :
x y
(seconds) (mph)
2 60
8 120
16 170
For x= 2 and x= 8 , the rate of change in function will be

For x= 8 and x= 16 , the rate of change in function will be

But 10 ≠ 6.25.
⇒ Rate of change is not constant.
It means the function non- linear.
Also , it is not a constant function because values of y is not constant w.r.t to x.
It is not a decreasing function because values of y increase with increase in x.