Exercise 8 Page 298

Let's start by recalling the general formula of exponential growth and exponential decay functions. cc Exponential Growth & Exponential Decay [0.8em] y=a(1+r)^t & y=a(1-r)^tIn both cases, a and r are positive numbers. For exponential decay, r is less than 1. Let's rewrite the given function to match one of the above formulas.

Our function matches the format of exponential decay. Here a= 80 and r= 0.4. y= 80(1- 0.4)^t This means that the rate of decay, also known as the percent of change, is 40 %.