Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 4 - Quadratic Functions - 4.4 Solving Quadratic Equations by the Square Root Property and Completing the Square - 4.4 Exercises - Page 349: 92

Answer

See graph

Work Step by Step

The function that we want to graph is shown below. Follow the steps outline to graph the function. $$ \begin{aligned} k(m) & =(m+2.5)^2-18.25. \end{aligned} $$ Step 1: We first determine the direction in which the function opens: The given function opens upward because the constant $a= 1$ is positive. Step 2: Determine the vertex and the equation for the axis of symmetry. The vertex is $(-2.5,-18.25)$ and the equation for the axis of symmetry is $x = -2.5$. Step 3: Find the $y$ and $x$ intercepts. To find the $y$ intercept, set $x= 0$ to find the value of $y$. Similarly, to find the $x$ intercept, set $ y= 0$ to find the values of $x$. $$ \begin{aligned} k(0)& =(0+2.5)^2-18.25\\ &= -12\\ \textbf{y-intercept: (0,-12)}. \end{aligned} $$ Set $ y = 0$ and solve. $$ \begin{aligned} (m+2.5)^2-18.25 & =0\\ (m+2.5)^2&= 18.25 \\ m+2.5& = \pm\sqrt{18.25}\\ m&= -2.5\pm \sqrt{18.25}. \end{aligned} $$ Find the two separate solutions: $$ \begin{array}{cl} m = -2.5 +\sqrt{18.25} &\text { or } m = -2.5 -\sqrt{18.25} \\ m= 1.77 & \text { or }\ m= -6.77\\ \textbf{x-intercept: (-6.77,0), (1.77,0)}. \end{array} $$ Step 4: Find the domain and range of the function and sketch it. Domain: All real numbers, Range: $[-18.25, \infty) $.
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