The graph of the exponential function varies depending on the value of the base . When , we get exponential growth which is always increasing:
However, when , we get exponential decay as which results in a function that is continually decreasing:
All base exponential graphs with the form have 3 common properties:
A horizontal asymptote at
A point going through
A point going through
Graphing General Exponentials
The general exponential equation can be written as:
Where are all constants.
We can follow 4 simple steps which should help us graph any exponential in this form.
Sketch a horizontal asymptote at
Find and mark out the point at , or in other words . This is the point where the exponential changes from being flat near the asymptote, to increasing / decreasing.
The “elbow” ( where the function begins increasing more rapidly ) of the regular exponential function occurs when . To generalise this concept to all exponentials, we are looking to solve for the value of which causes the exponent to equal zero.
Hence, to make the exponent of equal to zero, we can solve for that value to be:
We can therefore approximate the location of the elbow as the coordinate .
Substitute a large number into the exponential eg to find what the function approaches as . Mark this on the graph.
Sketch an exponential functions which goes through the marked points and has the corresponding asymptote.
An example with all the key-points is shown below.
Which we can visualize with the standard shape below:
It can be transformed into the form:
We can explain the effect of each parameter one-by-one:
controls the dilation of the graph
controls the dilation of the
moves the graph
moves the graph
It also controls the height of the asymptote
Drawing a Graph
To draw a quick graph of an exponential, you can always count on this technique:
Mark the horizontal asymptote at
Substitute to find the y-intercept at the point
Substitute any other value to find another point
Join the two points with a curve that approaches the asymptote
This technique makes it easy to graph anything we like.
Difficulty
00
Time
SOLUTION
Difficulty
2 Mins
Time
Graph , and on the same set of axes.
SOLUTION
To graph these functions we will note that they all go through the points and where is the base of that exponential.
Exponentials with different bases.
Notice how a larger base corresponds to a steeper curve.
Difficulty
8 Mins
Time
Graph the following on different set of axes:
SOLUTION
Part A
Rearranging the equation gives
Using the graph we only have the transformation , which means we shift the graph down by 3 units.
A simple shift, first example
Part B
Using the graph we only have the transformation which shifts the graph to the right by 2 units.
A simple shift, second example
Part C
Rearranging the equation gives:
Using the graph we have two transformations, which shifts the graph to the left by 1 unit and which shifts the graph up by 2 units.
A simple shift, third example
Difficulty
4 Mins
Time
Graph
SOLUTION
Rearranging the equation gives:
Using the graph this gives us the transforms and . If we track the points (0, 0) and (1, 2):
X
0
1
x
1
2
Y
0
2
y
4
10
We can also see in our equation that approaches 0 as x approaches negative inifinity - so f(x) approaches 4 as x approaches negative infinity. This gives us the following graph.
An easy transformation
Difficulty
6 Mins
Time
Graph
SOLUTION
Rearranging the equation gives:
Using the graph this gives us the transforms and . If we track the points (0, 0) and (1, e):
X
0
1
x
2
1.5
Y
0
e
y
6
6 - 3e
We can also see in our equation that approaches 0 as x approaches negative positive - so f(x) approaches 6 as x approaches positive infinity. This gives us the following graph.
A hard tranformation
Difficulty
10 Mins
Time
A very common (and cool) looking graph that is very important in studying probability and statistics is called the bell curve. A simple version of the bell curve is:
If , rewrite in terms of .
Create a table of values of for x = -2, -1, -0.5, 0, 0.5, 1, 2.
Create a table of values of using the values found above.
What does approach as x approaches positive and negative infinity? Hence what does approach as x approaches positive and negative infinity?
Using parts c and d, graph the bell curve.
SOLUTION
Part A
We just need to replace in our equation with , hence:
Part B and C
x
-2
-1
-0.5
0
0.5
1
2
g(x)
-2
-0.5
-0.125
0
-0.125
-0.5
-2
f(x)
0.14
0.61
0.88
1
0.88
0.61
0.14
Part D Clearly, approaches negative infinity in both directions. Therefore, must approach 0 in both directions.
Part E
The bell curve graph
Difficulty
7 Mins
Time
Graph
SOLUTION
Rearranging the equation gives:
Using the graph this gives us the transforms and . If we track the points (0, 0) and (1, e):
X
0
1
x
6
4
Y
0
e
y
2
We can also see in our equation that approaches 0 as x approaches positive inifinity - so f(x) approaches 4 as x approaches positive infinity. This gives us the following graph.
A harder transformation
Homework will appear here once homework is set for this session
Edit Homework
Confirm
Clear All
Cancel
Presets
Exponential and Logarithmic Functions
Cambridge 2 Unit Year 11 | Exercise 7F
Question 2 (all)
Question 5 (all)
Question 6 (all)
Question 10 (a, b, e, f)
Lesson Loading
×
×
Graphing Exponentials
Review Questions
How do we graph exponentials in the form ?
Find the y-coordinates for and
Find the x-coordinates for and
Find the y-coordinates for and
Find the x-coordinates for and
What is the first step we should perform when trying to graph transformed exponentials?
Write in terms of and in terms of
Solve and so that and are the subjects
Rewrite the function in the form
What is the next step we should perform when trying to graph transformed exponentials?
Solve and so that and are the subjects
Rewrite the function in the form
Write in terms of and in terms of
What is the third step we should perform when trying to graph transformed exponentials?
Rewrite the function in the form
Write in terms of and in terms of
Solve and so that and are the subjects
Once we have the relations for and in a simplified form, what points were used to map the exponential over in the example?
We substituted and to find the value of . Then we substituted and to find
We substituted and to find the value of . Then we substituted and to find
We substituted and to find the value of . Then we substituted and to find
We substituted and to find the value of . Then we substituted and to find
×
Graphing Exponentials
Review Questions
How do we graph exponentials in the form ?
Find the y-coordinates for and
Find the x-coordinates for and
Find the y-coordinates for and
Find the x-coordinates for and
What is the first step we should perform when trying to graph transformed exponentials?
Solve and so that and are the subjects
Rewrite the function in the form
Write in terms of and in terms of
What is the next step we should perform when trying to graph transformed exponentials?
Write in terms of and in terms of
Solve and so that and are the subjects
Rewrite the function in the form
What is the third step we should perform when trying to graph transformed exponentials?
Rewrite the function in the form
Solve and so that and are the subjects
Write in terms of and in terms of
Once we have the relations for and in a simplified form, what points were used to map the exponential over in the example?
We substituted and to find the value of . Then we substituted and to find
We substituted and to find the value of . Then we substituted and to find
We substituted and to find the value of . Then we substituted and to find
We substituted and to find the value of . Then we substituted and to find