Say a car's value drops 20% annually. In ﬁve years estimate
the percentage of the original vehicle value that is retained.
Assume you bought this vehicle at the time t = 0 (assume
the mileage of x = 0 km) for $ 20,000. Assume you drive about
15,000 km annualy (assume uniform driving habits over the year).
Let the input variable x be mileage of the car in km and the
output variable y = f(x) be the value of the car in dollars.
i. Find an expression for the function f(x) in terms of x.
The both equations need to be exponential, but I am having a difficult time figuring it out