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This lesson will discuss how to apply different transformations to exponential functions. Also, it will be seen how to identify these transformations in the graphs of different exponential functions.

### Catch-Up and Review

Here are a few recommended readings before getting started with this lesson.

Challenge

## Transforming a Function's Graph

The graph of the exponential function is drawn on the coordinate plane.

By applying transformations to the above graph, draw the graph of
Discussion

## Exponential Parent Function

The exponential function with and is the exponential parent function. This is the most basic function of the family. The graph of this function is shown for positive values of less than
Next, the graph of is shown for values of grater than
Discussion

## Reflection of Exponential Functions

A reflection of a function is a transformation that flips a graph over a line called the line of reflection. A reflection in the axis is achieved by changing the sign of every output value. This means changing the sign of the coordinate of every point on the graph of a function. Consider the exponential parent function
This reflection can be shown on a coordinate plane.
A reflection in the axis is instead achieved by changing the sign of every input value.
This transformation can also be shown on a coordinate plane.
Example

## Reflecting an Exponential Function

Tiffaniqua is beginning to explore the graphs of exponential functions.

She is interested in the graph of the exponential function

By reflecting this exponential parent function on the corresponding axis, she wants to draw the graphs of the following functions.

a
b

a
b

### Hint

a Recall that the graph of is a reflection of the graph of in the axis.
b The graph of is a reflection of the graph of in the axis.

### Solution

a The graph of is a reflection of the graph of in the axis. Therefore, the graph of is a reflection of the graph of in the axis.
b The graph of is a reflection of the graph of in the axis. Therefore, the graph of is a reflection of the graph of in the axis.
Explore

## Stretching and Shrinking a Graph

In the coordinate plane, the graph of the exponential function can be seen. By changing the values of and observe how the graph is vertically and horizontally stretched and shrunk.

Discussion

## Stretch and Shrink of Exponential Functions

A function graph is vertically stretched or shrunk by multiplying the output of a function rule by some positive constant Consider the exponential parent function
If is greater than the graph is vertically stretched by a factor of Conversely, if is less than the graph is vertically shrunk by a factor of If then there is no stretch nor shrink. All vertical distances from the graph to the axis are changed by the factor
Similarly, a function graph is horizontally stretched or shrunk by multiplying the input of a function rule by some positive constant
In this case, if is greater than the graph is horizontally shrunk by a factor of Conversely, if is less than the graph is horizontally stretched by a factor of If then there is neither a stretch nor shrink of the graph.
Example

## Finding the Equation of a Stretch and a Shrink

Tiffaniqua, feeling good, continues her study of exponential functions.

She considers the exponential parent function and wants to write the function rules of two functions.

a An exponential function whose graph is a vertical stretch of the graph of by a factor of
b An exponential function whose graph is a horizontal shrink of the graph of by a factor of

### Hint

a A function graph is vertically stretched or shrunk by multiplying the function rule by a positive constant.
b A function graph is horizontally stretched or shrunk by multiplying the input of a function rule by a positive constant.

### Solution

a A function graph is vertically stretched or shrunk by multiplying the function rule by a positive constant. If the constant is greater than the graph is vertically stretched. Therefore, if the graph of the given function is to be vertically stretched by a factor of the function rule must be multiplied by
This can be seen in a coordinate plane.
b A function graph is horizontally stretched or shrunk by multiplying the input of the function rule by a positive constant. If the constant is greater than the graph is horizontally shrunk. Therefore, to horizontally shrink the graph by a factor of the input of the function rule must be multiplied by
This can be seen in a coordinate plane.
Pop Quiz

## Stating the Factor of a Stretch or a Shrink

The graph of the exponential parent function is shown in the coordinate plane. The graph of a horizontal or vertical stretch or shrink is also shown.

Example

## Combining Transformations of Exponential Functions

On her quest to figure out exponential functions, Tiffaniqua has met her match.

She is thinking about the exponential parent function and wants to write the function rules of two functions.

a First, she wants write an exponential function whose graph is a vertical shrink by a factor of followed by a reflection in the axis of the graph of
b Next, she wants to write an exponential function whose graph is a horizontal stretch by a factor of followed by a reflection in the axis of the graph of

### Hint

a A function graph is vertically stretched or shrunk by multiplying the function rule by a positive constant. Furthermore, a function graph is reflected in the axis by changing the sign of the input.
b A function graph is horizontally stretched or shrunk by multiplying the input of the function rule by a positive constant. Furthermore, a function graph is reflected in the axis by changing the sign of the coordinate of every point on the graph.

### Solution

a A function graph is vertically stretched or shrunk by multiplying the function rule by a positive constant. If the constant is less than the graph is vertically shrunk. Therefore, if the graph of the given function is to be vertically shrunk by a factor of the function rule must be multiplied by
Furthermore, a function graph is reflected in the axis by changing the sign of the input.
This can be seen in a coordinate plane.
b A function graph is horizontally stretched or shrunk by multiplying the input of the function rule by a positive constant. If the constant is less than the graph is horizontally stretched. Therefore, to horizontally stretch the graph by a factor of the input of the function rule must be multiplied by
Furthermore, a function graph is reflected in the axis by changing the sign of the coordinate of every point on the graph.
This can be seen in a coordinate plane.
Explore

## Translating a Graph

In the coordinate plane, the graph of the function can be seen. By changing the values of and observe how the graph is horizontally and vertically translated.

Discussion

## Translation of Exponential Functions

A translation of a function is a transformation that shifts a graph vertically or horizontally. A vertical translation is achieved by adding some number to every output value of a function rule. Consider the exponential parent function
If is a positive number, the translation is performed upwards. Conversely, if is negative, the translation is performed downwards. If then there is no translation. This transformation can be shown on a coordinate plane.
A horizontal translation is instead achieved by subtracting a number from every input value.
In this case, if is a positive number, the translation is performed to the right. Conversely, if is negative, the translation is performed to the left. If then there is no translation. This transformation can also be shown on a coordinate plane.
Example

## Translating an Exponential Function

Tiffaniqua is feeling good about her understanding of the graphs of exponential functions. She is now moving on to mastering another aspect of them.

With translations on her mind, Tiffaniqua has drawn the graph of the exponential function

By translating this exponential parent function, she wants to draw the graphs and write the equations of the following functions.

a A translation of the graph of two units down.
b A translation of the graph of one unit to the left.
c A translation of the graph of two units up and three units to the right.

a Equation:

Graph:

b Equation:

Graph:

c Equation:

Graph:

### Hint

a The graph of is a vertical translation of the graph of by units. If is positive, the translation is upwards. If is negative, the translation is downwards.
b The graph of is a horizontal translation of the graph of by units. If is positive, the translation is to the right. If is negative, the translation is to the left.
c The graph of is a horizontal translation followed by a vertical translation by and units, respectively.

### Solution

a The graph of is a vertical translation of the graph of by units. If is positive, the translation is upwards. Conversely, if is negative, then the translation is downwards.
This can be seen on the coordinate plane.
b The graph of is a horizontal translation of the graph of by units. If is positive, the translation is to the right. Conversely, if is negative, then the translation is to the left.
This can be seen on the coordinate plane.
c The graph of is a horizontal translation followed by a vertical translation by and units, respectively. If is positive the horizontal translation is to the right, and if is negative this translation is to the left. Similarly, if is positive, the vertical translation is upwards. If is negative, this translation is downwards.
This can be seen on the coordinate plane.
Pop Quiz

## Stating the Translation

The graph of the exponential parent function and a vertical or horizontal translation are shown in the coordinate plane.

Closure

## Transforming a Function's Graph

With the topics learned in this lesson, the challenge presented at the beginning can be solved. The graph of the exponential function is given.

By applying transformations to the above graph, draw the graph of