A used car has a value of $15,250 when it is purchased in 2012. The value of the car depreciates at a rate of 7.5% per year. How do you write an exponential function that models the value of the car, y, over x years?
When something is depreciating at a fixed percent (in this case 7.5% per year) we use the formula
Where a is the initial value ($15,250) and the rate is written as a decimal (always the case in these models). T represents time in this case, in the number of years that passes.