1. 8.1& 8.2 Exponential Growth and Decay Functions
EQ1: What do we need to know about the graphs of exponential functions?
EQ2: How can we tell the difference between growth and decay problems?

2. EQ: How can we tell the difference between growth and decay problems?
Exponential Models
Growth: Decay:
y = final amount
P = initial amount
t = time in years
r = % of increase
1+r = growth factor
y = final amount
P = initial amount
t = time in years
r = % of decrease
1- r = decay factor
EQ: How can we tell the difference between growth and decay problems?

3. EQ: How can we tell the difference between growth and decay problems?
Basically…
If the number raised to a power is GREATER than 1, then it is a GROWTH function.
If the number raised to a power is LESS than 1, then it is a DECAY function.
The growth/decay factor is the number raised to a power!
EQ: How can we tell the difference between growth and decay problems?

4. EQ: How can we tell the difference between growth and decay problems?
In 2005, the cost of tuition at a state university was $6,000. During the next 5 years, the tuition is expected to rise 4% each year.
Write a model the gives the tuition y (in dollars) t years after 2005.
What is the growth factor?
How much would it cost to attend college in 2008? In 2010?
EQ: How can we tell the difference between growth and decay problems?

5. EQ: How can we tell the difference between growth and decay problems?
A certain car depreciates at a rate of 11% per year. It was purchased new in 2006 for $32000.
Write a model the gives the value of the car y (in dollars) t years after 2006
What is the decay factor?
How much is the car worth now? In 2012?
Estimate the year the car be worth approximately $4560.
EQ: How can we tell the difference between growth and decay problems?

6. Compound Interest $ For n compoundings per year:
You need to know this box!!
A = balance (final amount)
P = principle (initial amount)
t = time in years
r = annual interest rate – DECIMAL form
n = times compounded per year $

7. a) quarterly b) monthly
A total of $ 12,000 is invested at an annual interest rate of 9%. Find the balance after 5 years if it is compounded
a) quarterly b) monthly
= $18,726.11
= $18,788.17 $

8. Homework Day 1:
pg. 469 #19-24 all; even; 43-45, 49-51,
and all
Day 2: Pg. 477 #19-24 all;
43-55 all; 67