8-2 Properties of Exponential
Functions
p. 431
Do Now
Does the function represent growth or decay?
What is the percent of increase or decrease?
y
3 x
 5( 2 )
a=5
b = 3/2
GREATHER THAN 1!
Example 1
Make a table of
values for ANY
exponential
function!
Graph.
y  6(.2)
x2
1
6.00
x
y
-2
5.00
-1
0.20
0
-0.76
1
-0.95
2
-0.99
5.00
4.00
3.00
2.00
1.00
0.00
-2.5
-2
-1.5
-1
-0.5
0
-1.00
-2.00
0.5
1
1.5
2
2.5
e
• e is a real number constant that is useful for
describing exponential growth or decay.
CONTINUOUSLY COMPOUNDED INTEREST FORMULA:
Constant
A=
rt
Pe
Annual
interest rate
Amount in
the account
Principal
amount
Time in years
Example 2
Suppose you invest $1300 at an annual interest
rate of 4.3% compounded continuously. Find
the amount in the account after 3 years.
rt
.043(3)
Pe
AA==(1300)e
= $1479
A=?
P = 1300
r = .043
t=3
Example 3
Sodium-24 has a half-life of 15 hours. How
much sodium-24 will you have after 60 hours
if your original sample is 64mg?
Let y = the amount of sodium-24
Let x = the number of hours elapsed
y
1
 64( 2 )
1
x
15
AWAYS ½!
How many half-lives in a 60
hour period?
1
 64( 2 )
 4mg
60
15
Homework
• p. 426 #1-33 every other odd
• p. 434 #1-25 every other odd