Exponential
Functions
When you are done with this
section, you will be able to do the following
- Sketch
the graph of an exponential function.
- Find basic characteristics of an exponential function (domain,
range,
intercepts, increasing/decreasing behavior).
- Write
formulas of transformed exponential functions,
- Use
an exponential model to solve an application problem (in particular,
models involving the natural exponential function and compound interest
formulas).
- Use
the compound interest formula to solve finance problems.
We are now moving on to a new type of
function. For this function, instead of raising the variable to a
power, we will raise a number to a variable. This type of
function is called an exponential function. Exponential functions
have several uses. They are used to describe populations growth,
radioactive decay, and compound interest.
A good place to find information about exponential functions
is
your text book (pages 379-397 in College
Algebra 3rd edition by Stewart, Redlin,
and Watson).
Read carefully:
- x-intercepts
are found in the
same way we found x-intercepts before (set the function equal
to 0 and solve). All x-intercepts are of the form (x,
0). A non-transformed exponential
function will have no x-intercepts.
- y-intercepts are found by plugging in 0 for x and
solving. All y-intercepts are of the form (0, y).
- The book mentions the "natural"
exponential function. This is just like all other exponential
functions. Its base is the number e.
- You will want to take note of when an
exponential function is increasing and when an exponential function is
decreasing.
Additional Exponential Functions Resources
On-line Resources:
Exponent Review
Exponential Functions
Homework:
The Exponential Functions Homework contains 7
problems.
Things to remember:
- Domains
must be written as
intervals. [ and ] indicate that the endpoint is included.
( and ) indicate that the endpoint is not included. Click
here for a review of interval notation.
- Intercepts are points and must be written as ordered pairs (x-intercepts
look like (x, 0) and y-intercepts look like (0, y)).
- The range of a function is all possible output values.
Ranges must be
written as
intervals. [ and ] indicate that the endpoint is included.
( and ) indicate that the endpoint is not included. Click
here for a review of interval notation.
- NEVER round
until the end of your problem.
- ALWAYS put
parentheses around your exponent. If your answer is correct when
you plug in 1 and not for any of the others, lack of parentheses is the
most likelyproblem.
Homework
examples:
Example
1: similar to problem 5
Example 2: similar to problem 6
Example 3: can help with problems 3 and 4
For this particular topic,
there are not
additional also recommended homework problems.
© 2005 Elizabeth E. K. Jones and the ASU
Department of
Mathematics and Statistics - All rights reserved.