Question: how to find the percent increase of an exponential function?
Answer: Then, the decay percent is 75%. y= 0.8(1.8)^x. The equation represents exponential growth because the growth factor is greater than 1. ==> 1+r = 1.8. ... 
Then, the growth percent is 80% y= 17(1/5)^x. The equation represents exponential decay because 1/5 is less than 1. ==> 1-r = 1/5. ... 
Then, the decay percent is 80%