2. Exponential Decay Functions
 Much like exponential growth
functions, they have the form f(x) = abx, but
instead have 0 < b < 1.
 Decide whether each is an exponential
growth or exponential decay function:

3. What’s the Shape?
 Let’s make a table to find the general shape.
 If we use as an example:
x
-3
-2
-1
0
1
2
3

4. To graph (when 0 < b < 1):
 Same as for b > 1, but curve is drawn from
right to left.
 Graph now approaches the x-axis on the
right side (instead of the left side).
 Example:
Graph

5. Example:
 Graph

6. Your Turn!
 Graph

7. General Exponential Functions
 General form:
 Same as before:
 Sketch parent graph
 Shift using h and k
 Example:
Graph
 Domain:
 Range:

8. Your Turn!
 Graph the function and state the domain
and range.

9. Exponential Decay Models
 For quantities that decrease by a fixed
percent each year, the amount after t years
is:
where a is the initial amount and r is the
percent decrease.
 (1 – r) is the decay factor

10. Example
 You buy a new car for $24,000. The value
of the car decreases by 6% each year.
 Write an exponential decay model that
describes the situation.
 What will be the value of the car after 2
years?

11. Your Turn!
 From 1982 to 1993, the number of records
sold in the US decreased by 61% per year.
There were 265 million records sold in
1982.
 Write an exponential decay model.
 How many records were sold in 1991?