Which parent function is represented by the graph apex

Antonette Dela Cruz, Laura Pennington

Learn what a parent function is by understanding the definition and types of parent functions. Explore parent function examples, graphs, and transformations. Updated: 05/22/2022

In mathematics, functions are defined as a relationship between input (independent variable such as x) and an output (dependent variable such as y). This relationship is in terms of rules describing the changes done to the input to create the output. Every function in math can be identified as a member of a family. The parent function of a family of functions is the simplest one in that family.

Mathematically, the parent function definition is a function in its most basic form that shows the relationship between the independent and dependent variables in their pre-transformed state. Transformations may be added from this basic form and change the equation into a more complicated form. These changes will create new equations that still follow the basic characteristics of the parent function.

Essentially, the properties that are shared among the family of functions that share a parent function are:

  1. the shape of their graphs
  2. the degree or the highest exponent
  3. the number of roots or solutions

Parent Functions

When you hear the term parent function, you may be inclined to think of two functions who love each other very much creating a new function.

Parent Function
Which parent function is represented by the graph apex

Well, that's not exactly right; however, there are some similarities that we can observe between our own parents and parent functions. In mathematics, we have certain groups of functions that are called families of functions. Just like our own families have parents, families of functions also have a parent function.

The similarities don't end there! In the same way that we share similar characteristics, genes, and behaviors with our own family, families of functions share similar algebraic properties, have similar graphs, and tend to behave alike. An example of a family of functions are the quadratic functions. All quadratic functions have a highest exponent of 2, their graphs are all parabolas so they have the same shape, and they all share certain characteristics.

Quadratic Family of Functions
Which parent function is represented by the graph apex

As mentioned above, each family of functions has a parent function. A parent function is the simplest function that still satisfies the definition of a certain type of function. For example, when we think of the linear functions which make up a family of functions, the parent function would be y = x. This is the simplest linear function.

Furthermore, all of the functions within a family of functions can be derived from the parent function by taking the parent function's graph through various transformations. These transformations include horizontal shifts, stretching or compressing vertically or horizontally, reflecting over the x or y axes, and vertical shifts. For example, in the above graph, we see that the graph of y = 2x^2 + 4x is the graph of the parent function y = x^2 shifted one unit to the left, stretched vertically, and shifted down two units. These transformations don't change the general shape of the graph, so all of the functions in a family have the same shape and look similar to the parent function.

Algebraically, these transformations correspond to adding or subtracting terms to the parent function and to multiplying by a constant. For example, the function y = 2x^2 + 4x can be derived by taking the parent function y = x^2, multiplying it by the constant 2, and then adding the term 4x to it.

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What are the Types of Parent Functions?

Examples of parent functions and their graphs are shown in Fig. 1.

Fig. 1 Graphs and equations of parent functions.

Which parent function is represented by the graph apex

The most basic functions are these parent functions, each with its set of properties and characteristics:

LINEAR FUNCTIONS

Fig. 2 Graph of a linear parent function.

Which parent function is represented by the graph apex
  • Equation of parent function: {eq}f(x) = x {/eq}
  • Graph is a straight line.
  • Equation may be written in standard, slope-intercept, or point-slope form.
  • Domain and range of parent function are all real numbers.
QUADRATIC FUNCTIONS

Fig. 3 Graph of a quadratic parent function

Which parent function is represented by the graph apex
  • Equation of parent function: {eq}f(x)=x^{2} {/eq}
  • Graph is a U-shaped curve called a parabola
  • Equation may be written in a standard form or factored form
  • The highest exponent is two, and the expected number of roots is two.
  • Domain of parent function is all real numbers. The range of parent function is {eq}[0,\infty ) {/eq}
CUBIC

Fig. 4 Graph of cubic parent function

Which parent function is represented by the graph apex
  • Equation of the parent function: {eq}f(x)=x^{3} {/eq}
  • The highest exponent is three, expected number of roots is three.
  • Graph shape is a unique "standing wiggle."
  • Domain and range are all real numbers
ABSOLUTE VALUE

Fig. 5 Graph of absolute value parent function

Which parent function is represented by the graph apex
  • Equation of the parent function: {eq}f(x)=|x| {/eq}
  • Graph of the function has a unique V-shaped graph
  • Equation has the unique operator "| |."
  • Domain of parent function is all real numbers. The range of parent function is {eq}[0,\infty ) {/eq}
RECIPROCAL

Fig. 6 Graph of a reciprocal parent function

Which parent function is represented by the graph apex
  • Equation of the parent function: {eq}f(x)=\frac{1}{x} {/eq}
  • Graph has horizontal and vertical asymptotes
  • Domain and range of the parent function can never be zero
EXPONENTIAL

Fig. 7 Graph of an exponential parent function

Which parent function is represented by the graph apex
  • Equation of the parent function: {eq}f(x)= e^{x} {/eq}
  • Graph has a horizontal asymptote
  • Domain is the set of all real numbers, and range is the set of positive y-values
LOGARITHMIC

Fig. 8 Graph of logarithmic parent function

Which parent function is represented by the graph apex
  • Equation of the parent function: {eq}f(x)= ln (x) {/eq}
  • Domain of {eq}(0,\infty ) {/eq}
  • Equations have the unique operators ln and log.
SQUARE ROOT

Fig. 9 Graph of a square root parent function.

Which parent function is represented by the graph apex
  • Equation of the parent function: {eq}f(x)=\sqrt{x} {/eq}
  • Domain and range are both {eq}[0,\infty ) {/eq}
  • Has a vertical asymptote
  • Has the radical symbol in its equations
TANGENT

Fig. 10 Graph of a tangent parent function

Which parent function is represented by the graph apex
  • Equation of the parent function: {eq}f(x)=tan(x) {/eq}
  • Has the unique operator tan in its equations.
  • Domain and range are all real numbers.
SINE

Fig. 11Graph of a sine parent function.

Which parent function is represented by the graph apex
  • Equation of parent fucntion: {eq}f(x)=sin(x) {/eq}
  • Graph is a sinusoidal curve
  • Equations have the operator "sin."
  • Domain is all real numbers, the range is {eq}[-1,1] {/eq}
COSINE

Fig. 12 Graph of a cosine parent function.

Which parent function is represented by the graph apex
  • Equation of parent function: {eq}f(x)=cos(x) {/eq}
  • Graph is a sinusoidal curve
  • Equations have the operator "cos."
  • Domain is all real numbers, the range is {eq}[-1,1] {/eq}

How are Parent Functions Identified and Transformed?

The parent functions may transform and change their equations to reflect all the new changes while at the same time still exhibiting the same graph and properties. These new functions can easily be classified under a parent function by understanding the changes.

Transformations add constants to the original parent function. Here are the places where changes could take place in a parent function equation:

{eq}f(x)\pm d {/eq}
  • This is a vertical translation, where +d moves the function up and -d moves it down d units
  • A constant may be added to or subtracted from the parent function (shown by the constant d)
  • This is easy to spot because it is separated from the original parent function with a plus or minus operator.
  • Example: {eq}f(x) = x + 2 {/eq} is part of the linear function family and transformed by moving up the parent function two units

Example: Exponential Functions

To illustrate this, let's consider exponential functions. Exponential functions are functions of the form y = ab^x, where a and b are both positive (greater than zero), and b is not equal to one. Basically, exponential functions are functions with the variable in the exponent. The number b is the base of the exponential function. Let's consider the family of functions that are exponential functions with base 2. Some functions that are in this family of functions are shown below.

Which parent function is represented by the graph apex

Notice that the simplest exponential function in the above family is y = 2^x. This is the parent function of the family of functions. In general, the simplest exponential function is y = b^x where b > 1. This is the parent function of exponential functions with base b. The graph below displays the graphs of all of the functions listed above. Observe that they all have the same shape as the parent function and that they can all be derived by performing the transformations previously mentioned to the parent function.

Exponential Family of Functions With Base 2
Which parent function is represented by the graph apex

Parent Functions

When you hear the term parent function, you may be inclined to think of two functions who love each other very much creating a new function.

Parent Function
Which parent function is represented by the graph apex

Well, that's not exactly right; however, there are some similarities that we can observe between our own parents and parent functions. In mathematics, we have certain groups of functions that are called families of functions. Just like our own families have parents, families of functions also have a parent function.

The similarities don't end there! In the same way that we share similar characteristics, genes, and behaviors with our own family, families of functions share similar algebraic properties, have similar graphs, and tend to behave alike. An example of a family of functions are the quadratic functions. All quadratic functions have a highest exponent of 2, their graphs are all parabolas so they have the same shape, and they all share certain characteristics.

Quadratic Family of Functions
Which parent function is represented by the graph apex

As mentioned above, each family of functions has a parent function. A parent function is the simplest function that still satisfies the definition of a certain type of function. For example, when we think of the linear functions which make up a family of functions, the parent function would be y = x. This is the simplest linear function.

Furthermore, all of the functions within a family of functions can be derived from the parent function by taking the parent function's graph through various transformations. These transformations include horizontal shifts, stretching or compressing vertically or horizontally, reflecting over the x or y axes, and vertical shifts. For example, in the above graph, we see that the graph of y = 2x^2 + 4x is the graph of the parent function y = x^2 shifted one unit to the left, stretched vertically, and shifted down two units. These transformations don't change the general shape of the graph, so all of the functions in a family have the same shape and look similar to the parent function.

Algebraically, these transformations correspond to adding or subtracting terms to the parent function and to multiplying by a constant. For example, the function y = 2x^2 + 4x can be derived by taking the parent function y = x^2, multiplying it by the constant 2, and then adding the term 4x to it.

Example: Exponential Functions

To illustrate this, let's consider exponential functions. Exponential functions are functions of the form y = ab^x, where a and b are both positive (greater than zero), and b is not equal to one. Basically, exponential functions are functions with the variable in the exponent. The number b is the base of the exponential function. Let's consider the family of functions that are exponential functions with base 2. Some functions that are in this family of functions are shown below.

Which parent function is represented by the graph apex

Notice that the simplest exponential function in the above family is y = 2^x. This is the parent function of the family of functions. In general, the simplest exponential function is y = b^x where b > 1. This is the parent function of exponential functions with base b. The graph below displays the graphs of all of the functions listed above. Observe that they all have the same shape as the parent function and that they can all be derived by performing the transformations previously mentioned to the parent function.

Exponential Family of Functions With Base 2
Which parent function is represented by the graph apex

How do you write a parent function?

The parent function is normally written in a very basic way, with just the independent and dependent variables and the correct degree or type of function (such as absolute value. For example, a linear function is just y=x. The quadratic parent function is just y=x^2.

What is a parent function in graphing?

The parent function in graphing is the basic equation where the graph is free from any transformation. For example, y=x is a parent function of a straight line. This graph may be translated, reflected, rotated, or dilated and the equations from such transformations will still be part of the family of lines.

What is a parent function and family example?

Functions may be classified and grouped into families. These groups each have one basic equation called a parent function. An example is the family of quadratic functions. This family shares the U-shaped graph called the parabola and they all have a second degree with the highest exponent.

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How do you find the parent function of a graph?

2. Explore the graphs of linear functions by adding or subtracting values to x (such as y(x) = x + 2) or by multiplying x by a constant (such as y(x) = 3x). Remember the linear parent function is y(x) = x. This is the most basic, simple form of the function.

Which parent function is represented by the graph absolute value parent function?

The parent function of absolute value functions is y = |x|. As shown from the parent function's graph, absolute value functions are expected to return V-shaped graphs.

What are the 5 parent functions?

These elementary functions include rational functions, exponential functions, basic polynomials, absolute values and the square root function.

Which of these is the quadratic parent function?

The parent function of a quadratic equation is y=x2 y = x 2 , whose graph has a vertex at the origin and experiences no vertical stretch or shrink.