Parent Functions and Transformations

This section covers:

(For Absolute Value Transformations, see the Absolute Value Transformations section.)

Before we get started, here are links to Parent Function Transformations in other sections:

You may not be familiar with all the functions and characteristics in the tables; here are some topics to review:

Basic Parent Functions

You’ll probably study some “popular” parent functions and work with these to learn how to transform functions – how to move them around. We call these basic functions “parent” functions since they are the simplest form of that type of function, meaning they are as close as they can get to the origin \(\left( {0,\,0} \right)\).

The chart below provides some basic parent functions that you should be familiar with. I’ve also included the anchor points, or critical points, the points with which to graph the parent function.

Know the shapes of these parent functions well! Even when using t-charts, you must know the general shape of the parent functions in order to know how to transform them correctly!

Parent Function Graph Parent Function Graph

\(y=x\)
Linear, Odd

Domain: \(\left( {-\infty ,\infty } \right)\)
Range: \(\left( {-\infty ,\infty } \right)\)

 

End Behavior**:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to -\infty \\x\to \infty \text{, }\,\,\,y\to \infty \end{array}\)

Critical points: \(\displaystyle \left( {-1,\,-1} \right),\,\left( {0,\,0} \right),\,\left( {1,\,1} \right)\)

\(y=\left| x \right|\)
Absolute Value, Even

Domain: \(\left( {-\infty ,\infty } \right)\)
Range: \(\left[ {0,\infty } \right)\)

 

End Behavior:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to \infty \\x\to \infty \text{, }\,\,\,y\to \infty \end{array}\)

Critical points: \(\displaystyle \left( {-1,\,1} \right),\,\left( {0,\,0} \right),\,\left( {1,\,1} \right)\)

\(y={{x}^{2}}\)
Quadratic, Even

Domain: \(\left( {-\infty ,\infty } \right)\)
Range: \(\left[ {0,\infty } \right)\)

 

End Behavior:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to \infty \\x\to \infty \text{, }\,\,\,y\to \infty \end{array}\)

Critical points:

\(\displaystyle \left( {-1,\,1} \right),\,\left( {0,\,0} \right),\,\left( {1,\,1} \right)\)

\(y=\sqrt{x}\)
Radical (Square Root), Neither

Domain: \(\left[ {0,\infty } \right)\)
Range: \(\left[ {0,\infty } \right)\)

 

End Behavior:
\(\displaystyle \begin{array}{l}x\to 0,\,\,\,\,y\to 0\\x\to \infty \text{, }\,\,\,y\to \infty \end{array}\)

Critical points:

\(\displaystyle \left( {0,\,0} \right),\,\left( {1,\,1} \right),\,\left( {4,\,2} \right)\)

\(y={{x}^{3}}\)
Cubic, Odd

Domain: \(\left( {-\infty ,\infty } \right)\)
Range: \(\left( {-\infty ,\infty } \right)\)

 

End Behavior:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to -\infty \\x\to \infty \text{, }\,\,\,y\to \infty \end{array}\)

Critical points:

\(\displaystyle \left( {-1,\,-1} \right),\,\left( {0,\,0} \right),\,\left( {1,\,1} \right)\)

\(y=\sqrt[3]{x}\)
Cube Root, Odd

Domain: \(\left( {-\infty ,\infty } \right)\)
Range: \(\left( {-\infty ,\infty } \right)\)

 

End Behavior:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to -\infty \\x\to \infty \text{, }\,\,\,y\to \infty \end{array}\)

Critical points:

\(\displaystyle \left( {-1,\,-1} \right),\,\left( {0,\,0} \right),\,\left( {1,\,1} \right)\)

\(\begin{array}{c}y={{b}^{x}},\,\,\,b>1\,\\(y={{2}^{x}})\end{array}\)

Exponential, Neither

Domain: \(\left( {-\infty ,\infty } \right)\)
Range: \(\left( {0,\infty } \right)\)

 

End Behavior:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to 0\\x\to \infty \text{, }\,\,\,y\to \infty \end{array}\)

Critical points:

\(\displaystyle \left( {-1,\,\frac{1}{b}} \right),\,\left( {0,\,1} \right),\,\left( {1,\,b} \right)\)

Asymptote:  \(y=0\)

\(\begin{array}{c}y={{\log }_{b}}\left( x \right),\,\,b>1\,\,\,\\(y={{\log }_{2}}x)\end{array}\)

Log, Neither

Domain: \(\left( {0,\infty } \right)\)
Range: \(\left( {-\infty ,\infty } \right)\)

 

End Behavior:
\(\begin{array}{l}x\to {{0}^{+}}\text{, }\,y\to -\infty \\x\to \infty \text{, }\,y\to \infty \end{array}\)

Critical points:

\(\displaystyle \left( {\frac{1}{b},\,-1} \right),\,\left( {1,\,0} \right),\,\left( {b,\,1} \right)\)

Asymptote: \(x=0\)

\(\displaystyle y=\frac{1}{x}\)

Rational (Inverse), Odd

Domain: \(\left( {-\infty ,0} \right)\cup \left( {0,\infty } \right)\)
Range: \(\left( {-\infty ,0} \right)\cup \left( {0,\infty } \right)\)

 

End Behavior:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to 0\\x\to \infty \text{, }\,\,\,y\to 0\end{array}\)

Critical points:

\(\displaystyle \left( {-1,\,-1} \right),\,\left( {1,\,1} \right)\)

Asymptotes: \(y=0,\,\,x=0\)

\(\displaystyle y=\frac{1}{{{{x}^{2}}}}\)

Rational (Inverse Squared),

         Even

Domain: \(\left( {-\infty ,0} \right)\cup \left( {0,\infty } \right)\)
Range: \(\left( {0,\infty } \right)\)

 

End Behavior:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to 0\\x\to \infty \text{, }\,\,\,y\to 0\end{array}\)

Critical points:

\(\displaystyle \left( {-1,\,1} \right),\,\left( {1,\,1} \right)\)

Asymptotes: \(x=0,\,\,y=0\)

\(y=\text{int}\left( x \right)=\left\lfloor x \right\rfloor \)

Greatest Integer*, Neither

Domain:\(\left( {-\infty ,\infty } \right)\)
Range: \(\{y:y\in \mathbb{Z}\}\text{ (integers)}\)

 

End Behavior:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to -\infty \\x\to \infty \text{, }\,\,\,y\to \infty \end{array}\)

Critical points:

\(\displaystyle \begin{array}{l}x:\left[ {-1,\,0} \right)\,\,\,y:-1\\x:\left[ {0,\,1} \right)\,\,\,y:0\\x:\left[ {1,\,2} \right)\,\,\,y:1\end{array}\)

 

\(y=C\)   (\(y=2\))

Constant, Even

Domain: \(\left( {-\infty ,\infty } \right)\)
Range: \(\{y:y=C\}\)

 

End Behavior:
\(\begin{array}{l}x\to -\infty \text{, }\,y\to C\\x\to \infty \text{, }\,\,\,y\to C\end{array}\)

Critical points:

\(\displaystyle \left( {-1,\,C} \right),\,\left( {0,\,C} \right),\,\left( {1,\,C} \right)\)

 

 

 

*The Greatest Integer Function, sometimes called the Step Function, returns the greatest integer less than or equal to a number (think of rounding down to an integer). There’s also a Least Integer Function, indicated by \(y=\left\lceil x \right\rceil \), which returns the least integer greater than or equal to a number (think of rounding up to an integer).

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**Notes on End Behavior: To get the end behavior of a function, we just look at the smallest and largest values of \(x\), and see which way the \(y\) is going. Not all functions have end behavior defined; for example, those that go back and forth with the \(y\) values and never really go way up or way down (called “periodic functions”) don’t have end behaviors.

Most of the time, our end behavior looks something like this:\(\displaystyle \begin{array}{l}x\to -\infty \text{, }\,y\to \,\,?\\x\to \infty \text{, }\,\,\,y\to \,\,?\end{array}\) and we have to fill in the \(y\) part. So the end behavior for a line with a positive slope is: \(\begin{array}{l}x\to -\infty \text{, }\,y\to -\infty \\x\to \infty \text{, }\,\,\,y\to \infty \end{array}\).

There are a couple of exceptions; for example, sometimes the \(x\) starts at 0 (such as in the radical function), we don’t have the negative portion of the \(x\) end behavior. Also, when \(x\) starts very close to 0 (such as in in the log function), we indicate that \(x\) is starting from the positive (right) side of 0 (and the \(y\) is going down); we indicate this by \(\displaystyle x\to {{0}^{+}}\text{, }\,y\to -\infty \).

Generic Transformations of Functions

Again, the “parent functions” assume that we have the simplest form of the function; in other words, the function either goes through the origin \(\left( {0,0} \right)\), or if it doesn’t go through the origin, it isn’t shifted in any way.

When a function is shifted, stretched (or compressed), or flipped in any way from its “parent function“, it is said to be transformed, and is a transformation of a function.

T-charts are extremely useful tools when dealing with transformations of functions. For example, if you know that the quadratic parent function \(y={{x}^{2}}\) is being transformed 2 units to the right, and 1 unit down (only a shift, not a stretch or a flip yet), we can create the original t-chart, following by the transformation points on the outside of the original points.Then we can plot the “outside” (new) points to get the newly transformed function:

Transformation T-chart Graph

Quadratic Function

 

\(y={{x}^{2}}\)

Transform function 2 units to the right, and 1 unit down.

   x + 2   x   y   y  – 1
      1    –1 1      0
      2      0 0    –1
      3      1 1      0

 

Transformed:

Domain:  \(\left( {-\infty ,\infty } \right)\)

Range:   \(\left[ {-1,\,\,\infty } \right)\)

 

When looking at the equation of the moved function, however, we have to be careful.

When functions are transformed on the outside of the \(f(x)\) part, you move the function up and down and do the “regular” math, as we’ll see in the examples below. These are vertical transformations or translations, and affect the \(y\) part of the function.

When transformations are made on the inside of the \(f(x)\) part, you move the function back and forth (but do the “opposite” math – since if you were to isolate the x, you’d move everything to the other side). These are horizontal transformations or translations, and affect the \(x\) part of the function.

There are several ways to perform transformations of parent functions; I like to use t-charts, since they work consistently with ever function. And note that in most t-charts, I’ve included more than just the critical points above, just to show the graphs better.

Vertical Transformations

Here are the rules and examples of when functions are transformed on the “outside” (notice that the \(y\) values are affected). The t-charts include the points (ordered pairs) of the original parent functions, and also the transformed or shifted points.

Notice that the first two transformations are translations, the third is a dilation, and the last are forms of reflections.

Note that absolute value transformations will be discussed more expensively in the Absolute Value Transformations Section!

Transformation What It Does Example Graph

\(f\left( x \right)+b\)

 

Translation

Move graph up  \(b\)  units

 

 

Every point on the graph is shifted up  \(b\)  units.

 

The \(x\)’s stay the same; add  \(b\)  to the \(y\) values.

Parent:

\(y={{x}^{2}}\)

Transformed: \(y={{x}^{2}}+ \,2\)

 

  x   y  y+2
–1 1    3
 0 0    2
 1 1    3

Domain:  \(\left( {-\infty ,\infty } \right)\)     Range:  \(\left[ {2,\,\,\infty } \right)\)

\(f\left( x \right)-b\)

 

Translation

Move graph down  \(b\)  units

 

 

Every point on the graph is shifted down  \(b\)  units.

 

The \(x\)’s stay the same; subtract  \(b\)  from the \(y\) values.

Parent:

\(y=\sqrt{x}\)

Transformed:

\(y=\sqrt{x}- \,3\)

 

x y   y–3
0 0   –3
1 1   –2
4 2   –1

Domain:  \(\left[ {0,\,\,\infty } \right)\)     Range: \(\left[ {-3,\,\,\infty } \right)\)

\(a\,\cdot f\left( x \right)\)

 

Dilation

Stretch graph vertically by a scale factor of  \(a\) (sometimes called a dilation).

 

 

Note that if \(a<1\), the graph is compressed or shrunk.

 

Every point on the graph is stretched  \(a\)  units.

 

The \(x\)’s stay the same; multiply the \(y\) values by \(a\).

Parent:

\(y={{x}^{3}}\)

Transformed:

\(y={{4x}^{3}}\)

 

  x   y   4y
–1 –1  –4
  0   0    0
  1   1    4

Domain: \(\left( {-\infty ,\infty } \right)\)     Range: \(\left( {-\infty ,\infty } \right)\)

\(-f\left( x \right)\)

 

Reflection

Flip graph around the \(x\)-axis.

 

 

Every point on the graph is flipped vertically.

 

The \(x\)’s stay the same; multiply the \(y\) values by \(-1\).

Parent:

\(y=\left| x \right|\)

Transformed:

\(y=-\left| x \right|\)

 

  x y   –y
–1 1   –1
  0 0     0
  1 1   –1

 

Domain: \(\left( {-\infty ,\infty } \right)\)     Range: \(\left( {-\infty ,\,\,0} \right]\)

\(\left| {f\left( x \right)} \right|\)

 

Absolute Value on the \(y\)

Reflect part of graph underneath the \(x\)-axis (negative \(y\)’s) across the \(x\)-axis. Leave positive \(y\)’s the same.

 

The \(x\)’s stay the same; take the absolute value of the \(y\)’s.

Parent:  \(y=\sqrt[3]{x}\)

 

Transformed: \(y=\left| {\sqrt[3]{x}} \right|\)

 

x  y   |y|
–1 –1    1
  0 0      0
  1 1      1

 

Domain:  \(\left( {-\infty ,\infty } \right)\)     Range:  \(\left[ {0,\infty } \right)\)

 

 

Horizontal Transformations

Here are the rules and examples of when functions are transformed on the “inside” (notice that the \(x\) values are affected). Notice that when the \(x\) values are affected, you do the math in the “opposite” way from what the function looks like: if you you’re adding on the inside, you subtract from the \(x\); if you’re subtracting on the inside, you add to the \(x\); if you’re multiplying on the inside, you divide from the \(x\); if you’re dividing on the inside, you multiply to the \(x\). If you have a negative value on the inside, you flip across the \(\boldsymbol{y}\) axis (notice that you still multiply the \(x\) by \(-1\) just like you do for with the \(y\) for vertical flips).

Notice that the first two transformations are translations, the third is a dilation, and the last are forms of reflections.

Note that absolute value transformations will be discussed more expensively in the Absolute Value Transformations Section!

(You may find it interesting is that a vertical stretch behaves the same way as a horizontal compression, and vice versa, since when stretch something upwards, we are making it skinnier.)

Transformation What It Does Example Graph
 \(f\left( {x+b} \right)\)

 

Translation

Move graph left  \(b\)  units

 

 

(Do the “opposite” when change is inside the parentheses or underneath radical sign.)

 

Every point on the graph is shifted left  \(b\)  units.

 

The \(y\)’s stay the same; subtract  \(b\)  from the \(x\) values.

Parent:

\(y={{x}^{2}}\)

Transformed:

\(y={{\left( {x+2} \right)}^{2}}\)

 

 x – 2    x y
   –3    –1 1
   –2      0 0
   –1      1 1

 

Domain: \(\left( {-\infty ,\infty } \right)\)     Range: \(\left[ {0,\,\,\infty } \right)\)

 \(f\left( {x-b} \right)\)

 

Translation

Move graph right  \(b\)  units

 

 

Every point on the graph is shifted right  \(b\)  units.

 

The \(y\)’s stay the same; add  \(b\)  to the \(x\) values.

Parent:

\(y=\sqrt{x}\)

Transformed:

\(y=\sqrt{{x- \,3}}\)

 

x + 3   x y
   3      0 0
   4      1 1
   7      4 2

 

Domain: \(\left[ {-3,\infty } \right)\)      Range: \(\left[ {0,\,\,\infty } \right)\)

 \(f\left( {a\cdot x} \right)\)

 

Dialation

Compress graph horizontally by a scale factor of  \(a\)  units (stretch or multiply by \(\displaystyle \frac{1}{a}\))

 

 

Every point on the graph is compressed  \(a\)  units horizontally.

 

The \(y\)’s stay the same; multiply the \(x\) values by \(\displaystyle \frac{1}{a}\).

 

Parent:

\(y={{x}^{3}}\)

 Transformed:

\(y={{\left( {4x} \right)}^{3}}\)

 

\(\frac{1}{4}x\)    x y
\(-\frac{1}{4}\)    –1 –1
    0      0 0
   \(\frac{1}{4}\)      1 1
 

Domain: \(\left( {-\infty ,\infty } \right)\)   Range: \(\left( {-\infty ,\infty } \right)\)

 \(f\left( {-x} \right)\)

 

Reflection

Flip graph around the \(y\) axis

 

 

Every point on the graph is flipped around the \(y\) axis.

 

The \(y\)’s stay the same; multiply the \(x\) values by \(-1\).

Parent:

\(y=\sqrt{x}\)

Transformed:

\(y=\sqrt{{-x}}\)

 

 –x       x y
   0      0 0
 –1      1 1
 –4      4 2

Domain:  \(\left( {-\infty ,0} \right]\)     Range: \(\left[ {0,\,\,\infty } \right)\)

\(f\left( {\left| x \right|} \right)\)

 

Absolute Value on the \(x\)

“Throw away” the negative \(x\)’s; reflect the positive \(x\)’s across the \(y\)-axis.

 

The positive \(x\)’s stay the same; the negative \(x\)’s take on the \(y\)’s of the positive \(x\)’s.

Parent: \(y=\sqrt{x}\)

 

Transformed:

\(y=\sqrt{{\left| x \right|}}\)

 

x y  New y
–4 NA     2
 –1 NA     1
  0 0
 1 1
 4 2

Domain:  \(\left( {-\infty ,\infty } \right)\)     Range:  \(\left[ {0,\infty } \right)\)

 

 

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Mixed Transformations

Most of the problems you’ll get will involve mixed transformations, or multiple transformations, and we do need to worry about the order in which we perform the transformations.

It usually doesn’t matter if we make the x changes or the y changes first, but within the \(x\)’s and \(y\)’s, we need to perform the transformations in the following order. Note that this is sort of similar to the order with PEMDAS (parentheses, exponents, multiplication/division, and addition/subtraction).

When performing these rules, the coefficients of the inside x must be 1; for example, we would need to have \(y={{\left( {4\left( {x+2} \right)} \right)}^{2}}\) instead of \(y={{\left( {4x+8} \right)}^{2}}\) (by factoring). If you didn’t learn it this way, see IMPORTANT NOTE below.

Here is the order:

  1. Perform Flipping across the axes first (negative signs).
  2. Perform Stretching and Shrinking next (multiplying and dividing).
  3. Perform Horizontal and Vertical shifts last (adding and subtracting).

But we can do steps 1 and 2 together (order doesn’t actually matter), since we can think of the first two steps as a “negative stretch/compression.”

I like to take the critical points and maybe a few more points of the parent functions, and perform all the transformations at the same time with a t-chart! We just do the multiplication/division first on the \(x\) or \(y\) points, followed by addition/subtraction. It makes it much easier!

Note again that since we don’t have an x “by itself” (coefficient of 1) on the inside, we have to get it that way by factoring! For example, we’d have to change \(y={{\left( {4x+8} \right)}^{2}}\text{ to }y={{\left( {4\left( {x+2} \right)} \right)}^{2}}\).

Let’s try to graph this “complicated” equation and I’ll show you how easy it is to do with a t-chart:

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\(\displaystyle f(x)=-3{{\left( {2x+8} \right)}^{2}}+10\)

(Note that for this example, we could move the \({{2}^{2}}\) to the outside to get a vertical stretch of \(3\left( {{{2}^{2}}} \right)=12\), but we can’t do that for many functions.)

We first need to get the \(x\) by itself on the inside by factoring, so we can perform the horizontal translations. This is what we end up with:

\(\displaystyle f(x)=-3{{\left( {2\left( {x+4} \right)} \right)}^{2}}+10\)

Now, what we need to do is to look at what’s done on the “outside” (for the \(y\)’s) and make all the moves at once, by following the exact math. Then we can look on the “inside” (for the \(x\)’s) and make all the moves at once, but do the opposite math. We do this with a t-chart.

We’re starting with the parent function \(f(x)={{x}^{2}}\). If we look at what we’re doing on the outside of what is being squared, which is the \(\displaystyle \left( {2\left( {x+4} \right)} \right)\), we’re flipping it across the \(x\)-axis (the minus sign), stretching it by a factor of 3, and adding 10 (shifting up 10). These are the things that we are doing vertically, or to the \(y\).

Now if we look at what we are doing on the inside of what we’re squaring, we’re multiplying it by 2, which means we have to divide by 2 (horizontal compression by a factor of \(\displaystyle \frac{1}{2}\)), and we’re adding 4, which means we have to subtract 4 (a left shift of 4). Remember that we do the opposite when we’re dealing with the \(x\).

Also remember that we always have to do the multiplication or division first with our points, and then the adding and subtracting (sort of like PEMDAS).

Note: You might see mixed transformations in the form \(\displaystyle g\left( x \right)=a\cdot f\left( {\left( {\frac{1}{b}} \right)\left( {x-h} \right)} \right)+k\), or with a coordinate rule \(\displaystyle \left( {x,\,y} \right)\to \left( {bx+h,\,\,ay+k} \right)\), where \(a\) is the vertical stretch, \(b\) is the horizontal stretch, \(h\) is the horizontal shift to the right, and \(k\) is the vertical shift upwards. For the transformation \(\displaystyle f(x)=-3{{\left( {2\left( {x+4} \right)} \right)}^{2}}+10\), we have \(a=-3\), \(\displaystyle b=\frac{1}{2}\,\,\text{or}\,\,.5\), \(h=-4\), and \(k=10\). Our transformation \(\displaystyle g\left( x \right)=-3f\left( {2\left( {x+4} \right)} \right)+10=g\left( x \right)=-3f\left( {\left( {\frac{1}{{\frac{1}{2}}}} \right)\left( {x-\left( {-4} \right)} \right)} \right)+10\) would be \({\left( {x,\,y} \right)\to \left( {.5x-4,\,-3y+10} \right)}\).

Here is the t-chart with the original function, and then the transformations on the outsides. Now we can graph the outside points (points that aren’t crossed out) to get the graph of the transformation.

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I’ve also included an explanation of how to transform this parabola without a t-chart, as we did in the Introduction to Quadratics section here.

t-chart Transformed Graph

Parent:  \(y={{x}^{2}}\)  (Quadratic)

 

 Transformed:  \(\displaystyle f(x)=-3{{\left( {2\left( {x+4} \right)} \right)}^{2}}+10\)

 y changes:      \(\displaystyle f(x)=\color{blue}{{-3}}{{\left( {2\left( {x+4} \right)} \right)}^{2}}\color{blue}{+10}\)  

 x changes:    \(\displaystyle f(x)=-3{{\left( {\color{blue}{2}\left( {x\text{ }\color{blue}{{+\text{ }4}}} \right)} \right)}^{2}}+10\)

 

Opposite for \(x\), “regular” for \(y\):

\(\left( {x,\,y} \right)\to \left( {.5x-4,\,-3y+10} \right)\)

 

  .5x4       x  y   –3y + 10
      –5        –2  4        –2
    –4.5         1  1          7
      –4          0  0        10
    –3.5         1  1          7
      –3          2  4        –2

 

Domain:    \(\left( {-\infty ,\infty } \right)\)   Range: \(\left( {-\infty ,10} \right]\)

How to graph without a t-chart:

Since this is a parabola and it’s in vertex form, the vertex of the transformation is \(\left( {-4,\,10} \right)\).

Notice that the coefficient of  is –12 (by moving the \({{2}^{2}}\) outside and multiplying it by the –3). Then the vertical stretch is 12, and the parabola faces down because of the negative sign.

The parent graph quadratic goes up 1 and over (and back) 1 to get two more points, but with a vertical stretch of 12, we go over (and back) 1 and down 12 from the vertex. Now we have two points to which you can draw the parabola from the vertex.

IMPORTANT NOTE In some books, for \(\displaystyle f\left( x \right)=-3{{\left( {2x+8} \right)}^{2}}+10\), they may NOT have you factor out the 2 on the inside, but just switch the order of the transformation on the \(\boldsymbol{y}\).

In these cases, the order of transformations would be horizontal shifts, horizontal reflections/stretches, vertical reflections/stretches, and then vertical shifts. For example, for this problem, you would move to the left 8 first for the \(\boldsymbol{y}\), and then compress with a factor of \(\displaystyle \frac {1}{2}\) for the \(\boldsymbol{x}\) (which is opposite of PEMDAS). Then you would perform the \(\boldsymbol{y}\) (vertical) changes the regular way – reflect and stretch by 3 first, and then shift up 10. So, you would have \(\displaystyle {\left( {x,\,y} \right)\to \left( {\frac{1}{2}\left( {x-8} \right),\,-3y+10} \right)}\). Try a t-chart; you’ll get the same t-chart as above!

Transformations in Function Notation (based on Graph and/or Points)

You may also be asked to perform a transformation of a function using a graph and individual points; in this case, you’ll probably be given the transformation in function notation. Note that we may need to use several points from the graph and “transform” them, to make sure that the transformed function has the correct “shape”.

Here are some examples; the second example is the transformation with an absolute value on the \(x\); see the Absolute Value Transformations section for more detail.

Original Graph and Points of Function

Transformation Example

Transformation Example

Function:

 

Domain: \(\left[ {-4,5} \right]\)      Range: \(\left[ {-7,5} \right]\)

 

 

 

Key Points:

  x    y
–4   5
 0   1
 2   2
 5 –7

 

Transformation:  \(\displaystyle f\left( {-\frac{1}{2}\left( {x-1} \right)} \right)-3\)

\(y\) changes: \(\displaystyle f\left( {-\frac{1}{2}\left( {x-1} \right)} \right)\color{blue}{{-\text{ }3}}\)

\(x\) changes:  \(\displaystyle f\left( {\color{blue}{{-\frac{1}{2}}}\left( {x\text{ }\color{blue}{{-\text{ }1}}} \right)} \right)-3\)

 

Note that this transformation flips around the \(\boldsymbol{y}\)axis, has a horizontal stretch of 2, moves right by 1, and down by 3.

 

 

Key Points Transformed:

(we do the “opposite” math with the “\(x\)”)

2x + 1      x   y       y – 3
      9         –4   5          2
      1           0   1        –2
    –3           2   2        –1
    –9           5 –7       –10

 

Transformed Function:

Domain:  \(\left[ {-9,9} \right]\)     Range: \(\left[ {-10,2} \right]\)

Transformation: \(\displaystyle f\left( {\left| x \right|+1} \right)-2\)

\(y\) changes:  \(\displaystyle f\left( {\left| x \right|+1} \right)\color{blue}{{\underline{{-\text{ }2}}}}\)

\(x\) changes:  \(\displaystyle f\left( {\color{blue}{{\underline{{\left| x \right|+1}}}}} \right)-2\):

 

Note that this transformation moves down by 2, and left 1. Then, for the inside absolute value, we will “get rid of” any values to the left of the \(y\)-axis and replace with values to the right of the \(y\)-axis, to make the graph symmetrical with the \(y\)-axis.

 

Let’s just do this one via graphs. First, move down 2, and left 1:

Then reflect the right-hand side across the \(y\)-axis to make symmetrical.

Transformed Function:

Domain:  \(\left[ {-4,4} \right]\)    Range:  \(\left[ {-9,0} \right]\)

Tricky!

 

Draw the points in the same order as the original to make it easier! And remember if you’re having trouble drawing the graph from the transformed ordered pairs, just take more points from the original graph to map to the new one!

Note: You may also be given a random point, say \(\left( {8,-2} \right)\), and give the transformed coordinates for the point of the graph \(y=-6g\left( {-2x} \right)-2\). To do this, to get the transformed \(y\), multiply the \(y\) part of the point by –6 and then subtract 2. To get the transformed \(x\), multiply the \(x\) part of the point by \(\displaystyle -\frac{1}{2}\) (opposite math). The new point is \(\left( {-4,\,10} \right)\).

Functional Notation Transformation Using Algebra

Let’s say we want to use a “function notation” transformation to transform a parent or non-parent equation. We can do this without using a t-chart, but by using substitution and algebra.

For example, if we want to transform \(f\left( x \right)={{x}^{2}}+4\) using the transformation \(\displaystyle -2f\left( {x-1} \right)+3\), we can just substitute “\(x-1\)” for “\(x\)” in the original equation, multiply by –2, and then add 3.

For example: \(\displaystyle -2f\left( {x-1} \right)+3=-2\left[ {{{{\left( {x-1} \right)}}^{2}}+4} \right]+3=-2\left( {{{x}^{2}}-2x+1+4} \right)+3=-2{{x}^{2}}+4x-7\).

We used this method to help transform a piecewise function here.

More Examples of Mixed Transformations:

Here are a couple more examples (using t-charts), with different parent functions.

Don’t worry if you are totally lost with the exponential and log functions; they will be discussed in the Exponential Functions and Logarithmic Functions sections.

Also, the last type of function is a rational function that will be discussed in the Rational Functions section.

Transformation T-chart/Domain and Range Graph

\(\displaystyle y=\frac{3}{2}{{\left( {-x} \right)}^{3}}+2\)

 

Parent function:

\(y={{x}^{3}}\)

 

For this function, note that could have also put the negative sign on the outside (thus affecting the \(y\)), and we would have gotten the same graph.

x    x y   \(\frac{3}{2}y+2\)
  1   –1 –1      .5
  0     0   0       2
–1     1   1     3.5

 

Domain:  \(\left( {-\infty ,\infty } \right)\)

Range: \(\left( {-\infty ,\infty } \right)\)

\(\displaystyle y=\frac{1}{2}\sqrt{{-x}}\)

 

Parent function:

\(y=\sqrt{x}\)

 x     x y    \(\frac{1}{2}y\)
    0     0 0     0
   –1     1 1    .5
   –4     4 2     1

 

Domain:  \(\left( {-\infty ,0} \right]\)

   Range: \(\left[ {0,\infty } \right)\)

\(y={{2}^{{x-4}}}+3\)

 

Parent function:

\(y={{2}^{x}}\)

 

For exponential functions, use –1, 0, and 1 for the \(x\) values for the parent function. (Easy way to remember: exponent is like \(x\)).

x + 4    x y    y + 3
    3    –1 .5    3.5
    4      0  1      4
    5      1  2      5

 

Domain:  \(\left( {-\infty ,\infty } \right)\)

Range:  \(\left( {3,\infty } \right)\)

Asymptote:  \(y=3\)

\(\begin{array}{l}y=\log \left( {2x-2} \right)-1\\y=\log \left( {2\left( {x-1} \right)} \right)-1\end{array}\)

 

Parent function:

\(y=\log \left( x \right)\)

 

For log and ln functions, use –1, 0, and 1 for the \(y\) values for the parent function.

 

(Note: for \(y={{\log }_{3}}\left( {2\left( {x-1} \right)} \right)-1\), for example, the \(x\) values for the parent function would be \(\displaystyle \frac{1}{3},\,\,1,\,\,\text{and}\,\,3\).)

.5x + 1   x  y    y – 1
 1.05      .1  1      –2
  1.5        1  0      –1
   6         10  1         0

 

Domain:  \(\left( {1,\infty } \right)\)

Range:  \(\left( {-\infty ,\infty } \right)\)

Asymptote:  \(x=1\)

\(\displaystyle y=\frac{3}{{2-x}}\,\,\,\,\,\,\,\,\,\,\,y=\frac{3}{{-\left( {x-2} \right)}}\)

 

Parent function:

\(\displaystyle y=\frac{1}{x}\)

–x + 2    x y     3y
3    –1 –1   –3
1      1 1     3

 

Domain: \(\left( {-\infty ,2} \right)\cup \left( {2,\infty } \right)\)

Range: \(\left( {-\infty ,0} \right)\cup \left( {0,\infty } \right)\)

Asymptotes: \(y=0\) and \(x=2\)

 

 

Here’s a mixed transformation with the Greatest Integer Function (sometimes called the Floor Function). Note how we can use intervals as the \(x\) values to make the transformed function easier to draw:

Transformation T-chart/Domain and Range Graph

\(\displaystyle y=\left[ {\frac{1}{2}x-2} \right]+3\)

\(\displaystyle y=\left[ {\frac{1}{2}\left( {x-4} \right)} \right]+3\)

 

Parent function:

\(y=\left[ x \right]\)

 

Note how we had to take out the \(\displaystyle \frac{1}{2}\) to make it in the correct form.

2x + 4        x   y   y + 3
  [0, 2)   [–2, –1) 2    1
  [2, 4)    [–1, 0) 1    2
 [4, 6)     [0, 1) 0     3
 [6, 8)     [1, 2) 1     4
 [8, 10)    [2, 3) 2     5

 

Domain:  \(\left( {-\infty ,\infty } \right)\)

Range:  \(\{y:y\in \mathbb{Z}\}\text{ (integers)}\)

Writing Transformed Equations from Graphs

You might be asked to write a transformed equation, give a graph. A lot of times, you can just tell by looking at it, but sometimes you have to use a point or two. And you do have to be careful and check your work, since the order of the transformations can matter.

Note that when figuring out the transformations from a graph, it’s difficult to know whether you have an “\(a\)” (vertical stretch) or a “\(b\)” (horizontal stretch) in the equation \(\displaystyle g\left( x \right)=a\cdot f\left( {\left( {\frac{1}{b}} \right)\left( {x-h} \right)} \right)+k\).

Sometimes the problem will indicate what parameters (\(a\), \(b\), and so on) to look for. For others, like polynomials (such as quadratics and cubics), a vertical stretch mimics a horizontal compression, so it’s possible to factor out a coefficient to turn a horizontal stretch/compression to a vertical compression/stretch.

(For more complicated graphs, you may want to take several points and perform a regression in your calculator to get the function, if you’re allowed to do that).

We will find a transformed equation from an absolute value graph in the Absolute Value Transformations section.

Here are some problems:

Graph Getting Equation
Write the general equation for the cubic equation in the form:  \(\displaystyle y={{\left( {\frac{1}{b}\left( {x-h} \right)} \right)}^{3}}+k\)

We see that that the center point, or critical point is at \(\left( {-4,\,-5} \right)\), so the cubic is in the form: \(\displaystyle y={{\left( {\frac{1}{b}\left( {x+4} \right)} \right)}^{3}}-5\).

 

Notice that to get back and over to the next points, we go back/over \(3\) and down/up \(1\), so we see there’s a horizontal stretch of \(3\), so \(b=3\). (It turns out that this is also a vertical compression of \(\displaystyle \frac{1}{{{{3}^{3}}}}=\frac{1}{{27}}\)).

 

So we have \(\displaystyle y={{\left( {\frac{1}{3}\left( {x+4} \right)} \right)}^{3}}-5\). Try it – it works!

Find the equation of this graph in any form:

 

Here’s a generic method you can typically use:

 

We see that this is a cubic polynomial graph (parent graph \(y={{x}^{3}}\)), but flipped around either the \(x\) the \(y\)-axis, since it’s an odd function; let’s use the \(x\)-axis for simplicity’s sake.

The equation will be in the form \(y=a{{\left( {x+b} \right)}^{3}}+c\), where \(a\) is negative, and it is shifted up \(2\), and to the left \(1\). Now we have \(y=a{{\left( {x+1} \right)}^{3}}+2\).

We need to find \(a\); use the point \(\left( {1,\,-10} \right)\):       \(\begin{align}-10&=a{{\left( {1+1} \right)}^{3}}+2\\-10&=8a+2\\8a&=-12;\,\,\,\,\,\,a=-\frac{{12}}{8}=-\frac{3}{2}\end{align}\)

The equation of the graph is: \(\displaystyle y=-\frac{3}{2}{{\left( {x+1} \right)}^{3}}+2\).

Be sure to check your answer by graphing or plugging in more points! √

Find the equation of this graph in any form:

 

The graph looks like a quadratic with vertex is \(\left( {-1,\,-8} \right)\), which is a shift of \(8\) down and \(1\) to the left. This will give us an equation of the form \(y=a{{\left( {x+1} \right)}^{2}}-8\), which is (not so coincidentally!) the vertex form for quadratics.

We need to find \(a\); use the point \(\left( {1,\,0} \right)\):    \(\begin{align}y&=a{{\left( {x+1} \right)}^{2}}-8\\\,\,\,\,0&=a{{\left( {1+1} \right)}^{2}}-8\\8&=4a;\,\,\,\,\,a=2\end{align}\) 

 

The equation of the graph then is: \(y=2{{\left( {x+1} \right)}^{2}}-8\).

 

Note: we could have also noticed that the graph goes over \(1\) and up \(2\) from the vertex, instead of over \(1\) and up \(1\) normally with \(y={{x}^{2}}\). This would mean that our vertical stretch is \(2\).

Find the equation of this graph with a base of .5 and horizontal shift of \(-1\):

 

We see that this exponential graph has a horizontal asymptote at \(y=-3\), and with the horizontal shift, we have \(y=a{{\left( {.5} \right)}^{{x+1}}}-3\) so far.

 

When you have a problem like this, first use any point that has a “0” in it if you can; it will be easiest to solve the system. Solve for \(a\) first using point \(\left( {0,-1} \right)\):

 

\(\begin{array}{c}y=a{{\left( {.5} \right)}^{{x+1}}}-3;\,\,\,-1=a{{\left( {.5} \right)}^{{0+1}}}-3;\,\,\,\,2=.5a;\,\,\,\,a=4\\y=4{{\left( {.5} \right)}^{{x+1}}}-3\end{array}\)

Rotational Transformations

You may be asked to perform a rotation transformation on a function (you usually see these in Geometry class). A rotation of 90° counterclockwise involves replacing \(\left( {x,\,y} \right)\) with \(\left( {-y,\,x} \right)\), a rotation of 180° counterclockwise involves replacing \(\left( {x,\,y} \right)\) with \(\left( {-x,\,-y} \right)\), and a rotation of 270° counterclockwise involves replacing \(\left( {x,\,y} \right)\) with \(\left( {y,\,-x} \right)\).

Here is an example:

Transformation Example Graph
Rotate graph 270° counterclockwise

Parent:  \(y={{x}^{2}}\)

 

Replace \((x,y)\) with \((y,–x)\)

 

y       x  y     x
4    –2 4      2
1    –1 1      1
0      0 0      0
1      1 1    –1
4      2 4    –2

 

Rotated Function Domain:  \(\left[ {0,\,\,\infty } \right)\)    Range:  \(\left( {-\infty ,\infty } \right)\)

 

 

Transformations of Inverse Functions

We learned about Inverse Functions here, and you might be asked to compare original functions and inverse functions, as far as their transformations are concerned. Remember that an inverse function is one where the \(x\) is switched by the \(y\), so the all the transformations originally performed on the \(x\) will be performed on the \(y\):

Problem:

If a cubic function is vertically stretched by a factor of 3, reflected over the y axis, and shifted down 2 units, what transformations are done to its inverse function?

Solution:

We need to do transformations on the opposite variable. So the inverse of this function will be horizontally stretched by a factor of 3, reflected over the \(x\) axis, and shifted to the left 2 units.

Here is a graph of the two functions:

Note that examples of Finding Inverses with Restricted Domains can be found here.

Applications of Parent Function Transformations

You may see a “word problem” that used Parent Function Transformations, and you may just have to use what you know about how to shift the functions (instead of coming up with the solution off the top of your head).

Here is an example:

Transformation Application Problem Solution
The following polynomial graph shows the profit that results from selling math books after September 1. The polynomial is \(p\left( x \right)=5{{x}^{3}}-20{{x}^{2}}+40x-1\), where \(x\) is the number of weeks after September 1.

 

The publisher of the math books were one week behind however;  describe how this new graph would look and what would be the new (transformed) function?

 

 

Since we’re moving the time in weeks by 1 week, we are shifting the graph horizontally, or shifting the inside, or \(x\) values.

 

Since our first profits will start a little after week 1, we can see that we need to move the graph to the right. When we move the \(x\) part to the right, we take the \(x\) values and subtract from them, so the new polynomial will be \(d\left( x \right)=5{{\left( {x-1} \right)}^{3}}-20{{\left( {x-1} \right)}^{2}}+40\left( {x-1} \right)-1\).

 

See how this was much easier, knowing what we know about transforming parent functions?

 

Learn these rules, and practice, practice, practice!


For Practice: Use the Mathway widget below to try a Transformation problem. Click on Submit (the blue arrow to the right of the problem) and click on Describe the Transformation to see the answer.

You can also type in your own problem, or click on the three dots in the upper right hand corner and click on “Examples” to drill down by topic.

If you click on Tap to view steps, or Click Here, you can register at Mathway for a free trial, and then upgrade to a paid subscription at any time (to get any type of math problem solved!).

On to Absolute Value Transformations – you are ready!

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