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4. Transformations of Radical Functions
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Chapter 3
4. 

Transformations of Radical Functions

This lesson explores the transformations of radical functions, focusing on square root functions. It discusses how these functions can be translated, stretched, or shrunk horizontally and vertically. Understanding these transformations is crucial in fields like engineering, physics, and computer graphics. For instance, in engineering, you might need to adjust the curve of a radical function to fit specific structural requirements. The lesson provides practical exercises and examples, helping you master the art of transforming radical functions for various applications.
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14 Theory slides
19 Exercises - Grade E - A
Each lesson is meant to take 1-2 classroom sessions
Transformations of Radical Functions
Slide of 14
This lesson will discuss how to apply different transformations to radical functions. It will also show how to identify these transformations in the graphs of different radical functions.
Challenge

Transforming the Graph of a Function

The graph of the parent function y=sqrt(x) and the graph of the radical function y=asqrt(x-h)+k are drawn on the same coordinate plane.

radical functions
Find the values of a, h, and k.
Explore

Translating a Graph

The graph of the function y=sqrt(x-h)+k is shown in the coordinate plane. By changing the values of h and k, observe how the graph is horizontally and vertically translated.

translating the graph of a radical function
Discussion

Translation of Radical Functions

A translation of a function is a transformation that shifts a graph vertically or horizontally. As with the graph of any other function, a vertical translation of the graph of a radical function is achieved by adding some number to every output value of the function rule. Consider the parent function y=sqrt(x). cc Function & Vertical Translation & bykUnits y=sqrt(x) & y=sqrt(x)+k If k is a positive number, the translation is performed upwards. Conversely, if k is negative, the translation is performed downwards. If k=0, then there is no translation. This transformation can be shown on a coordinate plane.

different values
A horizontal translation is instead achieved by subtracting a number from every input value. cc Function & Horizontal Translation & byhUnits y=sqrt(x) & y=sqrt(x-h) In this case, if h is a positive number, the translation is performed to the right. Conversely, if h is negative, the translation is performed to the left. If h=0, then there is no translation. This transformation can also be shown on a coordinate plane.
horizontal translation
Example

Translating Radical Functions

Ignacio has just started to learn about transformations of radical functions. In order to get some extra practice, he goes online to to find a worksheet for the topic. He found a pretty good exercise, which is divided into parts A, B, and C.
A) Write the equation and draw the graph of a function whose graph is a translation 3 units to the right of the graph of f(x)=2\sqrt{2x}-1. B) Write the equation and draw the graph of a function whose graph is a translation 5 units up of the graph of g(x)=0.5\sqrt{x+2}-3. C) Write the equation and draw the graph of a function whose graph is a translation 3 units down and 4 units to the left of the graph of h(x)=\sqrt{x-2}+3.
Help Ignacio solve the exercise!

Answer

a Equation: y=2sqrt(2x-6)-1

Graph:

Translation 3 units to the right
b Equation: y=0.5sqrt(x+2)+2

Graph:

Translation 5 units up
c Equation: y=sqrt(x+2)

Graph:

Translation 5 units up

Hint

a To translate the graph of f to the right 3 units, find an equation for f(x-3).
b To translate the graph of g up 5 units, find an equation for g(x)+5.
c To translate the graph of h down 3 units and to the left 4 units, find an equation for h(x+4)-3.

Solution

a To translate the graph of a function 3 units to the right, the number 3 must be subtracted from the input of the function.
Function f(x)=2sqrt(2x)-1 [1em] Translation3Units to the Right y=f(x - 3) ⇕ y=2sqrt(2(x - 3))-1 The right-hand side of the equation can be simplified by distributing the 2 in the radicand.
y=2sqrt(2(x-3))-1
y=2sqrt(2x-6)-1
Now both functions can be drawn on the same coordinate plane.
Translation 3 units to the right
b To translate the graph of a function 5 units up, the number 5 must be added to the output of the function.
Function g(x)=0.5sqrt(x+2)-3 [1em] Translation5Units Up y=g(x) + 5 ⇕ y=0.5sqrt(x+2)-3 + 5 The right-hand side of the equation can be simplified by adding the terms.
y=0.5sqrt(x+2)-3+5
y=0.5sqrt(x+2)+2
Now both functions can be drawn on the same coordinate plane.
Translation 5 units up
c To translate the graph of a function 3 units down and 4 units to the left, 3 must be subtracted from the output and 4 must be added to the input.
Function h(x)=sqrt(x-2)+3 [1em] Translation3Units Down and4Units to the Left y=h(x + 4) - 3 ⇕ y=sqrt(x + 4-2)+3 - 3 The right-hand side of the equation can be simplified by subtracting the terms.
y=sqrt(x+4-2)+3-3
y=sqrt(x+2)
Now both functions can be drawn on the same coordinate plane.
Translation 3 units down and 4 units to the left
Pop Quiz

Stating the Translation

The graphs of the rational function y=sqrt(x) and a vertical or horizontal translation are shown in the coordinate plane.

find the value of the constant
Explore

Stretching and Shrinking a Graph

The graph of the radical function y=asqrt(cx) is shown in the coordinate plane. By changing the values of a and c, observe how the graph is vertically and horizontally stretched and shrunk.

different values
Discussion

Stretch and Shrink of Radical Functions

A function graph is vertically stretched or shrunk by multiplying the output of the function rule by some positive constant a. Consider the radical function y=sqrt(x-1)+1. Function y=sqrt(x-1)+1 [1em] Vertical Stretch/Shrink by a Factor ofa y=a(sqrt(x-1)+1) ⇔ y=asqrt(x-1)+a If a is greater than 1, the graph is vertically stretched by a factor of a. Conversely, if a is less than 1, the graph is vertically shrunk by a factor of a. If a=1, then there is neither stretch nor shrink. All vertical distances from the graph to the x-axis are changed by the factor a.
different values
Similarly, the graph of a radical function is horizontally stretched or shrunk by multiplying the input of the function rule by some positive constant c. Consider this time the parent function y=sqrt(x). cc Function & Horizontal Stretch/Shrink & by a Factor ofc y=sqrt(x) & y=sqrt(cx) In this case, if c is greater than 1, the graph is horizontally shrunk by a factor of c. Conversely, if c is less than 1, the graph is horizontally stretched by a factor of c. If c=1, then there is neither a stretch nor shrink of the graph.
different values

Extra

Finding a and c

Suppose that a function is horizontally or vertically stretched/shrunk, and that the graphs of the transformed and the original function are both drawn on the same coordinate plane. Then, the values of a or c can be found by following these procedures.

Finding a Select two points with the same x-coordinate, one point P on the parent function and the other point Q on the transformed function. The value of a is the quotient of the y-coordinate of Q and the y-coordinate of P.
Finding c Select two points with the same y-coordinate, one point P on the parent function and the other point Q on the transformed function. The value of c is the quotient of the x-coordinate of P and the x-coordinate of Q.
Example

Stretching and Shrinking Radical Functions

After mastering vertical and horizontal translations of radical functions, Ignacio is having a hard time understanding vertical and horizontal stretches and shrinks of this type of function. He asked for some help from his very good friend Jordan.

Ignacio

In order to help him, Jordan asks Ignacio to consider the following function. f(x)=sqrt(x-1)+3 She then tells him to complete the next two exercises.

a Write the equation and draw the graph of a function whose graph is a vertical stretch of the graph of f by a factor of 4.
b Write the equation and draw the graph of a function whose graph is a horizontal shrink of the graph of f by a factor of 2.

Answer

a Equation: y=4sqrt(x-1)+12

Graph:

vertical stretch by a factor of 4
b Equation: y=sqrt(2x-1)+3

Graph:

horizontal shrink by a factor of 2

Hint

a To vertically stretch the graph of f by a factor of 4, multiply the output by 4.
b To horizontally shrink the graph of f by a factor of 2, multiply the input by 2.

Solution

a To vertically stretch the graph of f by a factor of 4, the output of the function must be multiplied by 4.
Function f(x)=sqrt(x-1)+3 [1em] Vertical Stretch by a Factor of4 y= 4f(x) ⇕ y= 4(sqrt(x-1)+3) The right-hand side of the function can be simplified by distributing the 4.
y=4(sqrt(x-1)+3)
y=4sqrt(x-1)+12
Now both functions can be drawn on the same coordinate plane.
vertical stretch by a factor of 4
b To horizontally shrink the graph of f by a factor of 2, the input of the function must be multiplied by 2.
Function f(x)=sqrt(x-1)+3 [1em] Horizontal Shrink by a Factor of2 y=f( 2x) ⇕ y=sqrt(2x-1)+3 Now both functions can be drawn on the same coordinate plane.
horizontal shrink by a factor of 2
Pop Quiz

Stating the Factor of Stretch or Shrink

The graph of the parent function y=sqrt(x) is shown in the coordinate plane. The graph of a horizontal or vertical stretch or shrink is also shown.

find the value of the constant
Discussion

Reflection of Radical 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 x-axis is achieved by changing the sign of every output value. This means changing the sign of the y-coordinate of every point on the graph of a function. Consider the radical function y=sqrt(x)+1. Function y=sqrt(x)+1 [1em] Reflection in thex-axis y=- (sqrt(x)+1 ) ⇔ y=- sqrt(x)-1 This reflection can be shown on a coordinate plane.
reflection on x-axis
A reflection in the y-axis is instead achieved by changing the sign of every input value. In this case, note that the domain of the radical function needs to be modified from all non-negative numbers to all non-positive numbers. Consider this time the parent function y=sqrt(x). cc Function & Reflection in they-axis y=sqrt(x) & y=sqrt(- x) This transformation can also be shown on a coordinate plane.
reflection on y-axis
Example

Reflecting Radical Functions

Ignacio is now feeling pretty confident about transformations of radical functions again. Now he turns his attention to reflections.

Salar Uyuni.jpeg

Ignacio considers the following radical function. f(x)=2sqrt(x-2)-1 He wants to answer two practice exercises about reflection of radical functions.

a Write the equation and draw the graph of a function whose graph is a reflection in the x-axis of the graph of f.
b Write the equation and draw the graph of a function whose graph is a reflection in the y-axis of the graph of f.

Answer

a Equation: y=- 2sqrt(x-2)+1

Graph:

b Equation: y=2sqrt(- x-2)-1

Graph:

Hint

a To reflect the graph of a function in the x-axis, multiply the output by - 1.
b To reflect the graph of a function in the y-axis, multiply the input by - 1.

Solution

a To reflect the graph of the given function in the x-axis, the output needs to be multiplied by - 1.
Function f(x)=2sqrt(x-2)-1 [1em] Reflection in thex-axis y= - f(x) ⇕ y= - (2sqrt(x-2)-1) The right-hand side of the function can be simplified by distributing the - 1.
y=- (2sqrt(x-2)-1)
y=- 2sqrt(x-2)+1
Now both functions can be graphed on the same coordinate plane.
reflection in the x-axis
b To reflect the graph of the given function in the y-axis, the input needs to be multiplied by - 1.
Function f(x)=2sqrt(x-2)-1 [1em] Reflection in they-axis y=f( - x) ⇕ y=2sqrt(- x-2)-1 Now, both functions can be graphed on the same coordinate plane.
reflection in the y-axis
Example

Combining Transformations

Ignacio confidently states that he can now solve any exercise about transformations of radical functions. Jordan skeptically challenges her friend to solve an exercise that combines transformations.

Ignacio and Jordan
Help Ignacio solve Jordan's challenge!

Answer

Equation: y=sqrt(- x+5)-6
Graph:

combination of transformations

Hint

Start by multiplying the output by 2 to find the function that represents the vertical stretch. Then, multiply the input by - 1 to reflect the graph in the y-axis. Finally, subtract 3 units from the input.

Solution

To help Ignacio, the transformations will be applied one at a time.

Vertical Stretch by a Factor of 2

First, the equation of the vertical stretch by a factor of 2 will be found. To do so, multiply the output of the function by 2. Function f(x)=0.5sqrt(x+2)-3 [1em] Vertical Stretch by a Factor of2 y= 2f(x) ⇕ y= 2(0.5sqrt(x+2)-3) Simplify the right-hand side of the above equation by distributing the 2.
y=2(0.5sqrt(x+2)-3)
y=1sqrt(x+2)-6
y=sqrt(x+2)-6
The graph of the function is a vertical stretch by a factor of 2 of the graph of f. Let g(x) be this function. g(x)=sqrt(x+2)-6

Reflection in the y-axis

To reflect the graph of a function in the y-axis, multiply the input by -1. Function g(x)=sqrt(x+2)-6 [1em] Reflection in they-axis y=g( -x) ⇕ y=sqrt(-x+2)-6 The graph of this function is a reflection in the y-axis of the graph of g. Let h(x) be this function. h(x)=sqrt(- x+2)-6

Translation 3 Units to the Right

Finally, to horizontally translate the graph of a function 3 units to the right, subtract 3 from the input. Function h(x)=sqrt(- x+2)-6 [1em] Translation3Units to the Right y=h(x - 3) ⇕ y=sqrt(- (x - 3)+2)-6 Simplify the right-hand side of the equation by distributing the - 1 and adding the terms in the radicand.
y=sqrt(- (x-3)+2)-6
y=sqrt(- x+3+2)-6
y=sqrt(- x+5)-6
The graph of this final function is a vertical stretch by a factor of 2, followed by a reflection in the y-axis, and a translation 3 units to the right of the graph of f.

Graph

The transformations can be shown on a coordinate plane.
combination of transformations
Closure

Transforming the Graph of a Function

With the topics learned in this lesson, the challenge presented at the beginning can be solved. The graphs of the radical function y=asqrt(x-h)+k and its corresponding parent function y=sqrt(x) are given.

radical functions
Find the values of a, h, and k.

Hint

Start by considering a vertical stretch. Then, consider vertical and horizontal translations.

Solution

Disregard translations for a moment. In the graph of y=sqrt(x) it can be understood as, after moving 1 unit to the right of the starting point (0,0), the graph increases vertically 1 unit. Conversely, in the graph of y=asqrt(x-h)+k, after moving 1 unit to the right of the starting point (- 3,0), the graph increased vertically 2 units.

radical functions


This means that the graph of y=asqrt(x-h)+k is a vertical stretch of the graph of y=sqrt(x) by a factor of 2. Therefore, the value of a is 2. cc Function & Vertical Stretch by & a Factor of2 y=sqrt(x) & y= 2sqrt(x) Next, pay close attention to the starting point of each curve. It can be concluded that the graph of the parent function y=sqrt(x) needs to be translated 3 units to the left to match the other graph. Therefore, the value of h is - 3. cc Function & Horizontal Translation & 3 Units to the Left y=2sqrt(x) & y=2sqrt(x-( - 3)) Finally, note that the y-coordinate of the initial point of both graphs is 0. Therefore, there is no vertical translation. This means that k= 0. cc Function & Vertical Translation & Units Up y = 2sqrt(x-(- 3)) & y = 2sqrt(x-(- 3)) + 0 It has been found that a= 2, h= - 3, and k= 0. The obtained function can be simplified.
y=2sqrt(x-(- 3)) + 0
y=2sqrt(x-(- 3))
y=2sqrt(x+3)
The transformations can be shown on a graph.
radical functions
Transformations of Radical Functions
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