{"id":1249,"date":"2015-11-12T18:35:30","date_gmt":"2015-11-12T18:35:30","guid":{"rendered":"https:\/\/courses.candelalearning.com\/collegealgebra1xmaster\/?post_type=chapter&#038;p=1249"},"modified":"2017-03-31T22:30:39","modified_gmt":"2017-03-31T22:30:39","slug":"describe-the-end-behavior-of-power-functions","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/chapter\/describe-the-end-behavior-of-power-functions\/","title":{"raw":"Describe the end behavior of power functions","rendered":"Describe the end behavior of power functions"},"content":{"raw":"<section id=\"fs-id1165137540446\">\r\n<h3>Identify power functions<\/h3>\r\n<p id=\"fs-id1165137570394\">In order to better understand the bird problem, we need to understand a specific type of function. A <strong>power function <\/strong>is a function with a single term that is the product of a real number, a <strong>coefficient,<\/strong> and a variable raised to a fixed real number. (A number that multiplies a variable raised to an exponent is known as a coefficient.)<\/p>\r\n<p id=\"fs-id1165135320417\">As an example, consider functions for area or volume. The function for the <strong>area of a circle<\/strong> with radius <em>r\u00a0<\/em>is<\/p>\r\n\r\n<div id=\"eip-544\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]A\\left(r\\right)=\\pi {r}^{2}[\/latex]<\/div>\r\n<p id=\"fs-id1165135191346\">and the function for the <strong>volume of a sphere<\/strong> with radius <em>r<\/em>\u00a0is<\/p>\r\n\r\n<div id=\"eip-640\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]V\\left(r\\right)=\\frac{4}{3}\\pi {r}^{3}[\/latex]<\/div>\r\n<p id=\"fs-id1165137579058\">Both of these are examples of power functions because they consist of a coefficient, [latex]\\pi [\/latex] or [latex]\\frac{4}{3}\\pi, [\/latex] multiplied by a variable <em>r<\/em>\u00a0raised to a power.<\/p>\r\n\r\n<div id=\"fs-id1165135356525\" class=\"note textbox\">\r\n<h3 class=\"title\">A General Note: Power Function<\/h3>\r\n<p id=\"fs-id1165137771947\">A <strong>power function<\/strong> is a function that can be represented in the form<\/p>\r\n\r\n<div id=\"eip-826\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]f\\left(x\\right)=k{x}^{p}[\/latex]<\/div>\r\n<p id=\"eip-id1165135584093\">where <em>k<\/em>\u00a0and <em>p<\/em>\u00a0are real numbers, and <em>k<\/em>\u00a0is known as the <strong>coefficient<\/strong>.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-id1165137661479\" class=\"note precalculus qa textbox\">\r\n<h3>Q &amp; A<\/h3>\r\n<p id=\"fs-id1165137582131\"><strong>Is [latex]f\\left(x\\right)={2}^{x}[\/latex] a power function?<\/strong><\/p>\r\n<p id=\"fs-id1165137598469\"><em>No. A power function contains a variable base raised to a fixed power. This function has a constant base raised to a variable power. This is called an exponential function, not a power function.<\/em><\/p>\r\n\r\n<\/div>\r\n<div id=\"Example_03_03_01\" class=\"example\">\r\n<div id=\"fs-id1165137745179\" class=\"exercise\">\r\n<div id=\"fs-id1165137742710\" class=\"problem textbox shaded\">\r\n<h3>Example 1: Identifying Power Functions<\/h3>\r\n<p id=\"fs-id1165137824370\">Which of the following functions are power functions?<\/p>\r\n<p id=\"fs-id1165137422594\" style=\"text-align: center\">[latex]\\begin{cases}f\\left(x\\right)=1\\hfill &amp; \\text{Constant function}\\hfill \\\\ f\\left(x\\right)=x\\hfill &amp; \\text{Identify function}\\hfill \\\\ f\\left(x\\right)={x}^{2}\\hfill &amp; \\text{Quadratic}\\text{ }\\text{ function}\\hfill \\\\ f\\left(x\\right)={x}^{3}\\hfill &amp; \\text{Cubic function}\\hfill \\\\ f\\left(x\\right)=\\frac{1}{x} \\hfill &amp; \\text{Reciprocal function}\\hfill \\\\ f\\left(x\\right)=\\frac{1}{{x}^{2}}\\hfill &amp; \\text{Reciprocal squared function}\\hfill \\\\ f\\left(x\\right)=\\sqrt{x}\\hfill &amp; \\text{Square root function}\\hfill \\\\ f\\left(x\\right)=\\sqrt[3]{x}\\hfill &amp; \\text{Cube root function}\\hfill \\end{cases}[\/latex]<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-id1165137422823\" class=\"solution textbox shaded\">\r\n<h3>Solution<\/h3>\r\n<p id=\"fs-id1165137843987\">All of the listed functions are power functions.<\/p>\r\n<p id=\"fs-id1165135533093\">The constant and identity functions are power functions because they can be written as [latex]f\\left(x\\right)={x}^{0}[\/latex] and [latex]f\\left(x\\right)={x}^{1}[\/latex] respectively.<\/p>\r\n<p id=\"fs-id1165137411464\">The quadratic and cubic functions are power functions with whole number powers [latex]f\\left(x\\right)={x}^{2}[\/latex] and [latex]f\\left(x\\right)={x}^{3}.[\/latex]<\/p>\r\n<p id=\"fs-id1165137475956\">The <strong>reciprocal<\/strong> and reciprocal squared functions are power functions with negative whole number powers because they can be written as [latex]f\\left(x\\right)={x}^{-1}[\/latex] and [latex]f\\left(x\\right)={x}^{-2}.[\/latex]<\/p>\r\n<p id=\"fs-id1165135704907\">The square and <strong>cube root<\/strong> functions are power functions with fractional powers because they can be written as [latex]f\\left(x\\right)={x}^{1\/2}[\/latex] or [latex]f\\left(x\\right)={x}^{1\/3}.[\/latex]<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"bcc-box bcc-info\">\r\n<h3>Try It 1<\/h3>\r\n<p id=\"fs-id1165137475225\">Which functions are power functions?<\/p>\r\n<p id=\"fs-id1165137824385\" style=\"text-align: center\">[latex]\\begin{cases}f\\left(x\\right)=2{x}^{2}\\cdot 4{x}^{3}\\hfill \\\\ g\\left(x\\right)=-{x}^{5}+5{x}^{3}-4x\\hfill \\\\ h\\left(x\\right)=\\frac{2{x}^{5}-1}{3{x}^{2}+4}\\hfill \\end{cases}[\/latex]<\/p>\r\n<a href=\"https:\/\/courses.candelalearning.com\/osprecalc\/chapter\/solutions-12\/\" target=\"_blank\">Solution<\/a>\r\n\r\n<\/div>\r\n<\/section><section id=\"fs-id1165134269023\"><\/section><section>\r\n<h3>Identify end behavior of power functions<\/h3>\r\n<p id=\"fs-id1165135436540\">Figure 2\u00a0shows the graphs of [latex]f\\left(x\\right)={x}^{2},g\\left(x\\right)={x}^{4}[\/latex] and [latex]h\\left(x\\right)={x}^{6},[\/latex] which are all power functions with even, whole-number powers. Notice that these graphs have similar shapes, very much like that of the quadratic function in the toolkit. However, as the power increases, the graphs flatten somewhat near the origin and become steeper away from the origin.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"487\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201324\/CNX_Precalc_Figure_03_03_0022.jpg\" alt=\"Graph of three functions, h(x)=x^2 in green, g(x)=x^4 in orange, and f(x)=x^6 in blue.\" width=\"487\" height=\"253\" \/> <b>Figure 2.<\/b> Even-power functions[\/caption]\r\n<p id=\"fs-id1165137911555\">To describe the behavior as numbers become larger and larger, we use the idea of infinity. We use the symbol [latex]\\infty[\/latex] for positive infinity and [latex]-\\infty[\/latex] for negative infinity. When we say that \"<em>x<\/em> approaches infinity,\" which can be symbolically written as [latex]x\\to \\infty,\\\\ [\/latex] we are describing a behavior; we are saying that <em>x<\/em>\u00a0is increasing without bound.<\/p>\r\n<p id=\"fs-id1165137658268\">With the even-power function, as the input increases or decreases without bound, the output values become very large, positive numbers. Equivalently, we could describe this behavior by saying that as [latex]x[\/latex] approaches positive or negative infinity, the [latex]f\\left(x\\right)[\/latex] values increase without bound. In symbolic form, we could write<\/p>\r\n\r\n<div id=\"eip-742\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]\\text{as }x\\to \\pm \\infty , f\\left(x\\right)\\to \\infty\\\\ [\/latex]<\/div>\r\n<p id=\"fs-id1165137533222\">Figure 3\u00a0shows the graphs of [latex]f\\left(x\\right)={x}^{3},g\\left(x\\right)={x}^{5},\\text{and}h\\left(x\\right)={x}^{7},[\/latex] which are all power functions with odd, whole-number powers. Notice that these graphs look similar to the cubic function in the toolkit. Again, as the power increases, the graphs flatten near the origin and become steeper away from the origin.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"312\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201325\/CNX_Precalc_Figure_03_03_0032.jpg\" alt=\"Graph of three functions, f(x)=x^3 in green, g(x)=x^5 in orange, and h(x)=x^7 in blue.\" width=\"312\" height=\"366\" \/> <b>Figure 3.<\/b> Odd-power function[\/caption]\r\n<p id=\"fs-id1165137730237\">These examples illustrate that functions of the form [latex]f\\left(x\\right)={x}^{n}[\/latex] reveal symmetry of one kind or another. First, in Figure 2\u00a0we see that even functions of the form [latex]f\\left(x\\right)={x}^{n}\\text{, }n\\text{ even,}[\/latex] are symmetric about the <em>y<\/em>-axis. In Figure 3\u00a0we see that odd functions of the form [latex]f\\left(x\\right)={x}^{n}\\text{, }n\\text{ odd,}[\/latex] are symmetric about the origin.<\/p>\r\n<p id=\"fs-id1165137812578\">For these odd power functions, as <em>x<\/em>\u00a0approaches negative infinity, [latex]f\\left(x\\right)[\/latex]\u00a0decreases without bound. As <em>x<\/em>\u00a0approaches positive infinity, [latex]f\\left(x\\right)[\/latex]\u00a0increases without bound. In symbolic form we write<\/p>\r\n\r\n<div id=\"eip-77\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]\\begin{cases}\\text{as } x\\to -\\infty , f\\left(x\\right)\\to -\\infty \\\\ \\text{as } x\\to \\infty , f\\left(x\\right)\\to \\infty \\end{cases}[\/latex]<\/div>\r\n<p id=\"fs-id1165137425284\">The behavior of the graph of a function as the input values get very small [latex](x\\to -\\infty)[\/latex] and get very large [latex](x\\to \\infty)[\/latex] is referred to as the <strong>end behavior<\/strong> of the function. We can use words or symbols to describe end behavior.<\/p>\r\n<p id=\"fs-id1165137433212\">The table\u00a0below shows the end behavior of power functions in the form [latex]f\\left(x\\right)=k{x}^{n}[\/latex] where [latex]n[\/latex] is a non-negative integer depending on the power and the constant.<span id=\"eip-id1165133101746\">\r\n<\/span><\/p>\r\n\r\n<table>\r\n<thead>\r\n<tr>\r\n<th><\/th>\r\n<th>Even power<\/th>\r\n<th>Odd power<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr>\r\n<td>\r\n<p style=\"text-align: center\">Positive constant<\/p>\r\n<p style=\"text-align: center\"><em>k<\/em> &gt; 0<\/p>\r\n<\/td>\r\n<td><a href=\"https:\/\/courses.candelalearning.com\/precalcone1xmommaster\/wp-content\/uploads\/sites\/1226\/2015\/08\/7.png\"><img class=\"alignnone size-full wp-image-12499\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201327\/7.png\" alt=\"7\" width=\"345\" height=\"460\" \/><\/a><\/td>\r\n<td><a href=\"https:\/\/courses.candelalearning.com\/precalcone1xmommaster\/wp-content\/uploads\/sites\/1226\/2015\/08\/8.png\"><img class=\"alignnone size-full wp-image-12500\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201327\/8.png\" alt=\"8\" width=\"301\" height=\"446\" \/><\/a><\/td>\r\n<\/tr>\r\n<tr>\r\n<td>\r\n<p style=\"text-align: center\">Negative constant<\/p>\r\n<p style=\"text-align: center\"><em>k<\/em> &lt; 0<\/p>\r\n<\/td>\r\n<td><a href=\"https:\/\/courses.candelalearning.com\/precalcone1xmommaster\/wp-content\/uploads\/sites\/1226\/2015\/08\/9.png\"><img class=\"alignnone size-full wp-image-12501\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201328\/9.png\" alt=\"9\" width=\"321\" height=\"460\" \/><\/a><\/td>\r\n<td><a href=\"https:\/\/courses.candelalearning.com\/precalcone1xmommaster\/wp-content\/uploads\/sites\/1226\/2015\/08\/10.png\"><img class=\"alignnone size-full wp-image-12502\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201330\/10.png\" alt=\"10\" width=\"326\" height=\"464\" \/><\/a><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<div id=\"fs-id1165135161436\" class=\"note precalculus howto textbox\">\r\n<h3 id=\"fs-id1165137415258\">How To: Given a power function [latex]f\\left(x\\right)=k{x}^{n}[\/latex] where <em>n<\/em>\u00a0is a non-negative integer, identify the end behavior.<\/h3>\r\n<ol id=\"fs-id1165137409522\">\r\n \t<li>Determine whether the power is even or odd.<\/li>\r\n \t<li>Determine whether the constant is positive or negative.<\/li>\r\n \t<li>Use Figure 4\u00a0to identify the end behavior.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<div id=\"Example_03_03_02\" class=\"example\">\r\n<div id=\"fs-id1165137923491\" class=\"exercise\">\r\n<div id=\"fs-id1165137599768\" class=\"problem textbox shaded\">\r\n<h3>Example 2: Identifying the End Behavior of a Power Function<\/h3>\r\n<p id=\"fs-id1165137644554\">Describe the end behavior of the graph of [latex]f\\left(x\\right)={x}^{8}.[\/latex]<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-id1165135169237\" class=\"solution textbox shaded\">\r\n<h3>Solution<\/h3>\r\nThe coefficient is 1 (positive) and the exponent of the power function is 8 (an even number). As <em>x<\/em>\u00a0approaches infinity, the output (value of [latex]f\\left(x\\right)[\/latex] ) increases without bound. We write as [latex]x\\to \\infty , f\\left(x\\right)\\to \\infty. [\/latex] As <em>x<\/em>\u00a0approaches negative infinity, the output increases without bound. In symbolic form, as [latex]x\\to -\\infty , f\\left(x\\right)\\to \\infty.\\\\ [\/latex] We can graphically represent the function as shown in Figure 5.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"487\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201331\/CNX_Precalc_Figure_03_03_0082.jpg\" alt=\"Graph of f(x)=x^8.\" width=\"487\" height=\"330\" \/> <strong>Figure 4<\/strong>[\/caption]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"Example_03_03_03\" class=\"example\">\r\n<div id=\"fs-id1165137535914\" class=\"exercise\">\r\n<div id=\"fs-id1165137811997\" class=\"problem textbox shaded\">\r\n<h3>Example 3: Identifying the End Behavior of a Power Function.<\/h3>\r\n<p id=\"fs-id1165137453217\">Describe the end behavior of the graph of [latex]f\\left(x\\right)=-{x}^{9}.[\/latex]<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-id1165137722696\" class=\"solution textbox shaded\">\r\n<h3>Solution<\/h3>\r\nThe exponent of the power function is 9 (an odd number). Because the coefficient is \u20131 (negative), the graph is the reflection about the <em>x<\/em>-axis of the graph of [latex]f\\left(x\\right)={x}^{9}.[\/latex] The graph\u00a0shows that as <em>x<\/em>\u00a0approaches infinity, the output decreases without bound. As <em>x<\/em>\u00a0approaches negative infinity, the output increases without bound. In symbolic form, we would write\r\n\r\n<img class=\"aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201332\/CNX_Precalc_Figure_03_03_0092.jpg\" alt=\"Graph of f(x)=-x^9.\" width=\"487\" height=\"667\" \/>\r\n<p style=\"text-align: center\"><strong>Figure 5.\u00a0<\/strong>[latex]\\begin{cases}\\text{as } x\\to -\\infty , f\\left(x\\right)\\to \\infty \\\\ \\text{as } x\\to \\infty , f\\left(x\\right)\\to -\\infty \\end{cases}[\/latex]<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-id1165135259565\" class=\"commentary\">\r\n<h3>Analysis of the Solution<\/h3>\r\n<p id=\"fs-id1165137548471\">We can check our work by using the table feature on a graphing utility.<\/p>\r\n\r\n<table id=\"Table_03_03_03\" summary=\"..\">\r\n<thead>\r\n<tr>\r\n<th><em>x<\/em><\/th>\r\n<th><em>f<\/em>(<em>x<\/em>)<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr>\r\n<td>\u201310<\/td>\r\n<td>1,000,000,000<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>\u20135<\/td>\r\n<td>1,953,125<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>0<\/td>\r\n<td>0<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>5<\/td>\r\n<td>\u20131,953,125<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>10<\/td>\r\n<td>\u20131,000,000,000<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<p id=\"fs-id1165137644426\">We can see from the table above\u00a0that, when we substitute very small values for <em>x<\/em>, the output is very large, and when we substitute very large values for <em>x<\/em>, the output is very small (meaning that it is a very large negative value).<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"bcc-box bcc-success\">\r\n<h3>Try It 2<\/h3>\r\n<p id=\"fs-id1165137734868\">Describe in words and symbols the end behavior of [latex]f\\left(x\\right)=-5{x}^{4}.[\/latex]<\/p>\r\n<a href=\"https:\/\/courses.candelalearning.com\/osprecalc\/chapter\/solutions-12\/\" target=\"_blank\">Solution<\/a>\r\n\r\n<\/div>\r\n<\/section><section id=\"fs-id1165134069294\"><\/section>","rendered":"<section id=\"fs-id1165137540446\">\n<h3>Identify power functions<\/h3>\n<p id=\"fs-id1165137570394\">In order to better understand the bird problem, we need to understand a specific type of function. A <strong>power function <\/strong>is a function with a single term that is the product of a real number, a <strong>coefficient,<\/strong> and a variable raised to a fixed real number. (A number that multiplies a variable raised to an exponent is known as a coefficient.)<\/p>\n<p id=\"fs-id1165135320417\">As an example, consider functions for area or volume. The function for the <strong>area of a circle<\/strong> with radius <em>r\u00a0<\/em>is<\/p>\n<div id=\"eip-544\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]A\\left(r\\right)=\\pi {r}^{2}[\/latex]<\/div>\n<p id=\"fs-id1165135191346\">and the function for the <strong>volume of a sphere<\/strong> with radius <em>r<\/em>\u00a0is<\/p>\n<div id=\"eip-640\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]V\\left(r\\right)=\\frac{4}{3}\\pi {r}^{3}[\/latex]<\/div>\n<p id=\"fs-id1165137579058\">Both of these are examples of power functions because they consist of a coefficient, [latex]\\pi[\/latex] or [latex]\\frac{4}{3}\\pi,[\/latex] multiplied by a variable <em>r<\/em>\u00a0raised to a power.<\/p>\n<div id=\"fs-id1165135356525\" class=\"note textbox\">\n<h3 class=\"title\">A General Note: Power Function<\/h3>\n<p id=\"fs-id1165137771947\">A <strong>power function<\/strong> is a function that can be represented in the form<\/p>\n<div id=\"eip-826\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]f\\left(x\\right)=k{x}^{p}[\/latex]<\/div>\n<p id=\"eip-id1165135584093\">where <em>k<\/em>\u00a0and <em>p<\/em>\u00a0are real numbers, and <em>k<\/em>\u00a0is known as the <strong>coefficient<\/strong>.<\/p>\n<\/div>\n<div id=\"fs-id1165137661479\" class=\"note precalculus qa textbox\">\n<h3>Q &amp; A<\/h3>\n<p id=\"fs-id1165137582131\"><strong>Is [latex]f\\left(x\\right)={2}^{x}[\/latex] a power function?<\/strong><\/p>\n<p id=\"fs-id1165137598469\"><em>No. A power function contains a variable base raised to a fixed power. This function has a constant base raised to a variable power. This is called an exponential function, not a power function.<\/em><\/p>\n<\/div>\n<div id=\"Example_03_03_01\" class=\"example\">\n<div id=\"fs-id1165137745179\" class=\"exercise\">\n<div id=\"fs-id1165137742710\" class=\"problem textbox shaded\">\n<h3>Example 1: Identifying Power Functions<\/h3>\n<p id=\"fs-id1165137824370\">Which of the following functions are power functions?<\/p>\n<p id=\"fs-id1165137422594\" style=\"text-align: center\">[latex]\\begin{cases}f\\left(x\\right)=1\\hfill & \\text{Constant function}\\hfill \\\\ f\\left(x\\right)=x\\hfill & \\text{Identify function}\\hfill \\\\ f\\left(x\\right)={x}^{2}\\hfill & \\text{Quadratic}\\text{ }\\text{ function}\\hfill \\\\ f\\left(x\\right)={x}^{3}\\hfill & \\text{Cubic function}\\hfill \\\\ f\\left(x\\right)=\\frac{1}{x} \\hfill & \\text{Reciprocal function}\\hfill \\\\ f\\left(x\\right)=\\frac{1}{{x}^{2}}\\hfill & \\text{Reciprocal squared function}\\hfill \\\\ f\\left(x\\right)=\\sqrt{x}\\hfill & \\text{Square root function}\\hfill \\\\ f\\left(x\\right)=\\sqrt[3]{x}\\hfill & \\text{Cube root function}\\hfill \\end{cases}[\/latex]<\/p>\n<\/div>\n<div id=\"fs-id1165137422823\" class=\"solution textbox shaded\">\n<h3>Solution<\/h3>\n<p id=\"fs-id1165137843987\">All of the listed functions are power functions.<\/p>\n<p id=\"fs-id1165135533093\">The constant and identity functions are power functions because they can be written as [latex]f\\left(x\\right)={x}^{0}[\/latex] and [latex]f\\left(x\\right)={x}^{1}[\/latex] respectively.<\/p>\n<p id=\"fs-id1165137411464\">The quadratic and cubic functions are power functions with whole number powers [latex]f\\left(x\\right)={x}^{2}[\/latex] and [latex]f\\left(x\\right)={x}^{3}.[\/latex]<\/p>\n<p id=\"fs-id1165137475956\">The <strong>reciprocal<\/strong> and reciprocal squared functions are power functions with negative whole number powers because they can be written as [latex]f\\left(x\\right)={x}^{-1}[\/latex] and [latex]f\\left(x\\right)={x}^{-2}.[\/latex]<\/p>\n<p id=\"fs-id1165135704907\">The square and <strong>cube root<\/strong> functions are power functions with fractional powers because they can be written as [latex]f\\left(x\\right)={x}^{1\/2}[\/latex] or [latex]f\\left(x\\right)={x}^{1\/3}.[\/latex]<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"bcc-box bcc-info\">\n<h3>Try It 1<\/h3>\n<p id=\"fs-id1165137475225\">Which functions are power functions?<\/p>\n<p id=\"fs-id1165137824385\" style=\"text-align: center\">[latex]\\begin{cases}f\\left(x\\right)=2{x}^{2}\\cdot 4{x}^{3}\\hfill \\\\ g\\left(x\\right)=-{x}^{5}+5{x}^{3}-4x\\hfill \\\\ h\\left(x\\right)=\\frac{2{x}^{5}-1}{3{x}^{2}+4}\\hfill \\end{cases}[\/latex]<\/p>\n<p><a href=\"https:\/\/courses.candelalearning.com\/osprecalc\/chapter\/solutions-12\/\" target=\"_blank\">Solution<\/a><\/p>\n<\/div>\n<\/section>\n<section id=\"fs-id1165134269023\"><\/section>\n<section>\n<h3>Identify end behavior of power functions<\/h3>\n<p id=\"fs-id1165135436540\">Figure 2\u00a0shows the graphs of [latex]f\\left(x\\right)={x}^{2},g\\left(x\\right)={x}^{4}[\/latex] and [latex]h\\left(x\\right)={x}^{6},[\/latex] which are all power functions with even, whole-number powers. Notice that these graphs have similar shapes, very much like that of the quadratic function in the toolkit. However, as the power increases, the graphs flatten somewhat near the origin and become steeper away from the origin.<\/p>\n<div style=\"width: 497px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201324\/CNX_Precalc_Figure_03_03_0022.jpg\" alt=\"Graph of three functions, h(x)=x^2 in green, g(x)=x^4 in orange, and f(x)=x^6 in blue.\" width=\"487\" height=\"253\" \/><\/p>\n<p class=\"wp-caption-text\"><b>Figure 2.<\/b> Even-power functions<\/p>\n<\/div>\n<p id=\"fs-id1165137911555\">To describe the behavior as numbers become larger and larger, we use the idea of infinity. We use the symbol [latex]\\infty[\/latex] for positive infinity and [latex]-\\infty[\/latex] for negative infinity. When we say that &#8220;<em>x<\/em> approaches infinity,&#8221; which can be symbolically written as [latex]x\\to \\infty,\\\\[\/latex] we are describing a behavior; we are saying that <em>x<\/em>\u00a0is increasing without bound.<\/p>\n<p id=\"fs-id1165137658268\">With the even-power function, as the input increases or decreases without bound, the output values become very large, positive numbers. Equivalently, we could describe this behavior by saying that as [latex]x[\/latex] approaches positive or negative infinity, the [latex]f\\left(x\\right)[\/latex] values increase without bound. In symbolic form, we could write<\/p>\n<div id=\"eip-742\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]\\text{as }x\\to \\pm \\infty , f\\left(x\\right)\\to \\infty\\\\[\/latex]<\/div>\n<p id=\"fs-id1165137533222\">Figure 3\u00a0shows the graphs of [latex]f\\left(x\\right)={x}^{3},g\\left(x\\right)={x}^{5},\\text{and}h\\left(x\\right)={x}^{7},[\/latex] which are all power functions with odd, whole-number powers. Notice that these graphs look similar to the cubic function in the toolkit. Again, as the power increases, the graphs flatten near the origin and become steeper away from the origin.<\/p>\n<div style=\"width: 322px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201325\/CNX_Precalc_Figure_03_03_0032.jpg\" alt=\"Graph of three functions, f(x)=x^3 in green, g(x)=x^5 in orange, and h(x)=x^7 in blue.\" width=\"312\" height=\"366\" \/><\/p>\n<p class=\"wp-caption-text\"><b>Figure 3.<\/b> Odd-power function<\/p>\n<\/div>\n<p id=\"fs-id1165137730237\">These examples illustrate that functions of the form [latex]f\\left(x\\right)={x}^{n}[\/latex] reveal symmetry of one kind or another. First, in Figure 2\u00a0we see that even functions of the form [latex]f\\left(x\\right)={x}^{n}\\text{, }n\\text{ even,}[\/latex] are symmetric about the <em>y<\/em>-axis. In Figure 3\u00a0we see that odd functions of the form [latex]f\\left(x\\right)={x}^{n}\\text{, }n\\text{ odd,}[\/latex] are symmetric about the origin.<\/p>\n<p id=\"fs-id1165137812578\">For these odd power functions, as <em>x<\/em>\u00a0approaches negative infinity, [latex]f\\left(x\\right)[\/latex]\u00a0decreases without bound. As <em>x<\/em>\u00a0approaches positive infinity, [latex]f\\left(x\\right)[\/latex]\u00a0increases without bound. In symbolic form we write<\/p>\n<div id=\"eip-77\" class=\"equation unnumbered\" style=\"text-align: center\">[latex]\\begin{cases}\\text{as } x\\to -\\infty , f\\left(x\\right)\\to -\\infty \\\\ \\text{as } x\\to \\infty , f\\left(x\\right)\\to \\infty \\end{cases}[\/latex]<\/div>\n<p id=\"fs-id1165137425284\">The behavior of the graph of a function as the input values get very small [latex](x\\to -\\infty)[\/latex] and get very large [latex](x\\to \\infty)[\/latex] is referred to as the <strong>end behavior<\/strong> of the function. We can use words or symbols to describe end behavior.<\/p>\n<p id=\"fs-id1165137433212\">The table\u00a0below shows the end behavior of power functions in the form [latex]f\\left(x\\right)=k{x}^{n}[\/latex] where [latex]n[\/latex] is a non-negative integer depending on the power and the constant.<span id=\"eip-id1165133101746\"><br \/>\n<\/span><\/p>\n<table>\n<thead>\n<tr>\n<th><\/th>\n<th>Even power<\/th>\n<th>Odd power<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\n<p style=\"text-align: center\">Positive constant<\/p>\n<p style=\"text-align: center\"><em>k<\/em> &gt; 0<\/p>\n<\/td>\n<td><a href=\"https:\/\/courses.candelalearning.com\/precalcone1xmommaster\/wp-content\/uploads\/sites\/1226\/2015\/08\/7.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-12499\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201327\/7.png\" alt=\"7\" width=\"345\" height=\"460\" \/><\/a><\/td>\n<td><a href=\"https:\/\/courses.candelalearning.com\/precalcone1xmommaster\/wp-content\/uploads\/sites\/1226\/2015\/08\/8.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-12500\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201327\/8.png\" alt=\"8\" width=\"301\" height=\"446\" \/><\/a><\/td>\n<\/tr>\n<tr>\n<td>\n<p style=\"text-align: center\">Negative constant<\/p>\n<p style=\"text-align: center\"><em>k<\/em> &lt; 0<\/p>\n<\/td>\n<td><a href=\"https:\/\/courses.candelalearning.com\/precalcone1xmommaster\/wp-content\/uploads\/sites\/1226\/2015\/08\/9.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-12501\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201328\/9.png\" alt=\"9\" width=\"321\" height=\"460\" \/><\/a><\/td>\n<td><a href=\"https:\/\/courses.candelalearning.com\/precalcone1xmommaster\/wp-content\/uploads\/sites\/1226\/2015\/08\/10.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-12502\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201330\/10.png\" alt=\"10\" width=\"326\" height=\"464\" \/><\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<div id=\"fs-id1165135161436\" class=\"note precalculus howto textbox\">\n<h3 id=\"fs-id1165137415258\">How To: Given a power function [latex]f\\left(x\\right)=k{x}^{n}[\/latex] where <em>n<\/em>\u00a0is a non-negative integer, identify the end behavior.<\/h3>\n<ol id=\"fs-id1165137409522\">\n<li>Determine whether the power is even or odd.<\/li>\n<li>Determine whether the constant is positive or negative.<\/li>\n<li>Use Figure 4\u00a0to identify the end behavior.<\/li>\n<\/ol>\n<\/div>\n<div id=\"Example_03_03_02\" class=\"example\">\n<div id=\"fs-id1165137923491\" class=\"exercise\">\n<div id=\"fs-id1165137599768\" class=\"problem textbox shaded\">\n<h3>Example 2: Identifying the End Behavior of a Power Function<\/h3>\n<p id=\"fs-id1165137644554\">Describe the end behavior of the graph of [latex]f\\left(x\\right)={x}^{8}.[\/latex]<\/p>\n<\/div>\n<div id=\"fs-id1165135169237\" class=\"solution textbox shaded\">\n<h3>Solution<\/h3>\n<p>The coefficient is 1 (positive) and the exponent of the power function is 8 (an even number). As <em>x<\/em>\u00a0approaches infinity, the output (value of [latex]f\\left(x\\right)[\/latex] ) increases without bound. We write as [latex]x\\to \\infty , f\\left(x\\right)\\to \\infty.[\/latex] As <em>x<\/em>\u00a0approaches negative infinity, the output increases without bound. In symbolic form, as [latex]x\\to -\\infty , f\\left(x\\right)\\to \\infty.\\\\[\/latex] We can graphically represent the function as shown in Figure 5.<\/p>\n<div style=\"width: 497px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201331\/CNX_Precalc_Figure_03_03_0082.jpg\" alt=\"Graph of f(x)=x^8.\" width=\"487\" height=\"330\" \/><\/p>\n<p class=\"wp-caption-text\"><strong>Figure 4<\/strong><\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"Example_03_03_03\" class=\"example\">\n<div id=\"fs-id1165137535914\" class=\"exercise\">\n<div id=\"fs-id1165137811997\" class=\"problem textbox shaded\">\n<h3>Example 3: Identifying the End Behavior of a Power Function.<\/h3>\n<p id=\"fs-id1165137453217\">Describe the end behavior of the graph of [latex]f\\left(x\\right)=-{x}^{9}.[\/latex]<\/p>\n<\/div>\n<div id=\"fs-id1165137722696\" class=\"solution textbox shaded\">\n<h3>Solution<\/h3>\n<p>The exponent of the power function is 9 (an odd number). Because the coefficient is \u20131 (negative), the graph is the reflection about the <em>x<\/em>-axis of the graph of [latex]f\\left(x\\right)={x}^{9}.[\/latex] The graph\u00a0shows that as <em>x<\/em>\u00a0approaches infinity, the output decreases without bound. As <em>x<\/em>\u00a0approaches negative infinity, the output increases without bound. In symbolic form, we would write<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/924\/2015\/11\/25201332\/CNX_Precalc_Figure_03_03_0092.jpg\" alt=\"Graph of f(x)=-x^9.\" width=\"487\" height=\"667\" \/><\/p>\n<p style=\"text-align: center\"><strong>Figure 5.\u00a0<\/strong>[latex]\\begin{cases}\\text{as } x\\to -\\infty , f\\left(x\\right)\\to \\infty \\\\ \\text{as } x\\to \\infty , f\\left(x\\right)\\to -\\infty \\end{cases}[\/latex]<\/p>\n<\/div>\n<div id=\"fs-id1165135259565\" class=\"commentary\">\n<h3>Analysis of the Solution<\/h3>\n<p id=\"fs-id1165137548471\">We can check our work by using the table feature on a graphing utility.<\/p>\n<table id=\"Table_03_03_03\" summary=\"..\">\n<thead>\n<tr>\n<th><em>x<\/em><\/th>\n<th><em>f<\/em>(<em>x<\/em>)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\u201310<\/td>\n<td>1,000,000,000<\/td>\n<\/tr>\n<tr>\n<td>\u20135<\/td>\n<td>1,953,125<\/td>\n<\/tr>\n<tr>\n<td>0<\/td>\n<td>0<\/td>\n<\/tr>\n<tr>\n<td>5<\/td>\n<td>\u20131,953,125<\/td>\n<\/tr>\n<tr>\n<td>10<\/td>\n<td>\u20131,000,000,000<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p id=\"fs-id1165137644426\">We can see from the table above\u00a0that, when we substitute very small values for <em>x<\/em>, the output is very large, and when we substitute very large values for <em>x<\/em>, the output is very small (meaning that it is a very large negative value).<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"bcc-box bcc-success\">\n<h3>Try It 2<\/h3>\n<p id=\"fs-id1165137734868\">Describe in words and symbols the end behavior of [latex]f\\left(x\\right)=-5{x}^{4}.[\/latex]<\/p>\n<p><a href=\"https:\/\/courses.candelalearning.com\/osprecalc\/chapter\/solutions-12\/\" target=\"_blank\">Solution<\/a><\/p>\n<\/div>\n<\/section>\n<section id=\"fs-id1165134069294\"><\/section>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-1249\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Precalculus. <strong>Authored by<\/strong>: Jay Abramson, et al.. <strong>Provided by<\/strong>: OpenStax. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/fd53eae1-fa23-47c7-bb1b-972349835c3c@5.175\">http:\/\/cnx.org\/contents\/fd53eae1-fa23-47c7-bb1b-972349835c3c@5.175<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Download For Free at : http:\/\/cnx.org\/contents\/fd53eae1-fa23-47c7-bb1b-972349835c3c@5.175.<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":276,"menu_order":2,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Precalculus\",\"author\":\"Jay Abramson, et al.\",\"organization\":\"OpenStax\",\"url\":\"http:\/\/cnx.org\/contents\/fd53eae1-fa23-47c7-bb1b-972349835c3c@5.175\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Download For Free at : http:\/\/cnx.org\/contents\/fd53eae1-fa23-47c7-bb1b-972349835c3c@5.175.\"}]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1249","chapter","type-chapter","status-publish","hentry"],"part":1238,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/pressbooks\/v2\/chapters\/1249","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/wp\/v2\/users\/276"}],"version-history":[{"count":9,"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/pressbooks\/v2\/chapters\/1249\/revisions"}],"predecessor-version":[{"id":2891,"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/pressbooks\/v2\/chapters\/1249\/revisions\/2891"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/pressbooks\/v2\/parts\/1238"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/pressbooks\/v2\/chapters\/1249\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/wp\/v2\/media?parent=1249"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/pressbooks\/v2\/chapter-type?post=1249"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/wp\/v2\/contributor?post=1249"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/ivytech-collegealgebra\/wp-json\/wp\/v2\/license?post=1249"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}