Functions will not always be linear or exponential but in this question there is 1 linear and 3 exponential answer choices:
An exponential function has the variable on the exponent.  A student in a classroom last year called it the “floating midget x”!
Let’s look at our options:
(1) compounded interest: exponential!!  Notice the formula has A = P (1+r)^t — that exponent makes it exponential and not linear!!
(2) doubling…hey that’s Moore’s Law: exponential function that makes the phone/computer you are reading this on exist!!
(3) cell phone service we could write the equation like this:  y = .20x + base  looks mighty like y = mx + b
(4) decay function is exponential as it also uses an exponent

The maximum of the above graph f(x) is 5 (when x = 1, y = 5)>
Let’s put g(x) into the TI-84:
Look at the graph below: definitely goes higher than the original graph and therefore has a larger maximum value.
Check out the table below — maximum y value is 11 which definitely beats 5!

This is really a slope question (average rate of change)
Look at the units: millimeters per year
So millimeters/years…millimeters divided by years
The average pupil diameter changed from 4.7 to 2.3
So -2.4mm is the change but over 60 years
We know it is 60 years from 20 to 80
-2.4mm/60 years

Try the provided values by substituting in for x.  We need to be careful about using parentheses when we enter the equation into Y=
We are looking for the x value that makes the equation equal 5/6