# GRAPHS OF EXPONENTIAL FUNCTIONS

GRAPHS OF EXPONENTIAL FUNCTIONS

By Nancy Marcus

In this section we will illustrate, interpret, and discuss the graphs of exponential functions. We will also illustrate how you can use graphs to HELP you solve exponential problems and check your answers.

Vertical Shifts: A vertical shift takes place when a function is shifted up or down. The following examples look at the difference between the graph of f(x) and the graph of f(x) + C.

Example 3: Graph the function and graph the function on the same rectangular coordinate system. Answer the following questions about each graph:

1.In what quadrants is the graph of the function located? In what quadrants is the graph of the function located?

2.What is the x-intercept and the y-intercept of the graph of the function ? What is the x-intercept and the y-intercept of the graph of the function ?

3.Find the point (2, f(2)) on the graph of and find (2, g(2)) on the graph of . What do these two points have in common? What is the difference between the two points.

4.Describe the relationship between the two graphs.

5.How would you move the graph of so that it is superimposed on the graph of ? After you move the graph, where would the point (0, 1) on be located?

6.Describe the difference between the two equations.

1.You can see that the both graphs are located in quadrants I and II. Therefore, both function values will always be positive.

2.You can see that from the graph that neither of the graphs crosses the x-axis; therefore, neither of the graphs has an x-intercept.

Note that the graph of f(x) crosses the y-axis at 1 because ; the graph of g(x) crosses the y-axis at 4 because .

3.The point , rounded to (2, 7.4) for graphing purposes, is located on the graph of .

The point , rounded to (2, 10.4) for graphing purposes, is located on the graph of . For each x-coordinate, the y-coordinates differ by 3.

4.Both graphs have the same shape. The graph of is nothing more than the graph of shifted up three units.

5.Shift (move) the graph of up 3 units. Every point on the graph of would be moved up 3 units. Therefore, the point (0, 1) would wind up at or after the move.

6.The only difference between the two equations is the + 3. The equations could be rewritten as follows: since . This means that for every value of x, the function g(x) will always be 3 units larger than the function f(x).

Example 4: Graph the function and the function on the same rectangular coordinate system. and answer the following questions about each graph:

1.In what quadrants is the graph of the function located? In what quadrants is the graph of the function located?

2.What is the x-intercept and the y-intercept of the graph of the function ? What is the x-intercept and the y-intercept of the graph of the function ?

3.Find the point (2, f(2)) on the graph of and find (2, g(2)) on the graph of . What do these two points have in common?

4.Describe the relationship between the two graphs.

5.Describe how you would shift (move) the graph of so that it is superimposed on the graph of . Where would the point (0, 1) on the graph of be located after the move?

6.What is the difference between the two equations?

1.The graph of is located in quadrants I and II. The graph of is located in quadrants I, III, and IV. This means that f(x) will always be positive, and g(x) can be positive, negative, and zero.

2.The graph of does not cross the x-axis. There is no x value such that will ever equal 0.

The graph of crosses the x-axis at 1.60943791243, rounded to 1.6 for graphing purposes:

Let and solve for x. Add 5 to both sides of the equation and we have . Take the natural logarithms of both sides of : or

3.The point , rounded to (2, 7.4) for graphing purposes, is located on the graph of .

4.The point , rounded to (2, 2.4) for graphing purposes, is located on the graph of . For each x-coordinate, the y-coordinates differ by 5.

5.Both graphs have the same shape. The graph of is nothing more than the graph of shifted down 5 units.

6.Shift (move) the graph of down five units so that it is superimposed on the graph of . When we move the graph of

down 5 units so that it is superimposed on the graph of . , every point on the graph of is shifted down 5 units. Therefore, the point (0, 1) will be shifted down to or .

7.The difference between the two equations is the - 5 because . The only substitution we made was to replace with f(x) in the equation . If we knew that the point (c, d) is located on the graph of f(x), we can conclude that the point (c, d - 5) is located on the graph of g(x). For every value of x, the function g(x) will always be 5 units less than the function f(x).

If you would like to review another example, click on Example.

[Exponential Rules] [Logarithms]

[Algebra] [Trigonometry ] [Complex Variables]