40 points, any guesses will be
function f is an exponential function. it predicts the value of a trading card, in hundreds of dollars, as a function of the number of decades since it was last purchased.

what equation models this function?

Step-by-step explanation:

Given graph models a function f which is an exponential function.

We know that the exponential function is given by  

, b is the rate of change and x is the time period.

In the given graph we see two points as (0,4) and (1,7)

Now, put x=0 and y=4 (for first point) in the exponential  function such that

Put x=1, y=7 and A=4 (for second point) in the exponential  function such that

Now substitute A=4 and b=1.75 in the standard exponential function we get our equation that models the given function that predicts the value of a trading card, in hundreds of dollars (y)

, where x is the number of decades.