Exponential Decay Functions

1
Exponential Decay Functions

• Goal Write and graph exponential decay functions.

2
12
10
20
A radioactive material decays at 10 per
year. How much of the 12 pound material will be
left after 20 years?
3
A car purchased for 24,500 will depreciate at a
rate of 18 per year for the first 6 years.
Write an equation and graph over the first 6
years.
30,000 20,000 10,000
1 2 3 4 5 6 7 8
4
Compare Growth and Decay Models
Exponential Growth
Exponential Decay
100 growth at 10 for 5 years.
100 depreciate at 10 for 5 years.
160 140 120 100 80 60 40 20
160 140 120 100 80 60 40 20
0 1 2 3 4 5
0 1 2 3 4 5
5
Classify each as exponential growth
or exponential decay.
1)
4)
Exponential Growth
Exponential Decay
2)
5)
Exponential Growth
Exponential Decay
3)
6)
Exponential Growth
Exponential Growth
6
Find the value of a downtown office building
that cost 12 million dollars to build 20 years
ago and depreciated at 9 per year.