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: 95

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. $$ \begin{aligned} f(t) &= 2(t-4)^2-44. \end{aligned} $$ Step 1: We first determine the direction in which the function opens: The given function opens upward because the constant $a= 2$ is positive. Step 2: Determine the vertex and the equation for the axis of symmetry. The vertex is $(4,-44)$ and the equation for the axis of symmetry is $x = 4$. 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 $x$. $$ \begin{aligned} f(0)& =2(0-4)^2-44\\ &= -12\\ &\text{y-intercept: (0,-12)}. \end{aligned} $$ Set $ y = 0$ and solve. $$ \begin{aligned} 2(t-4)^2-44 & =0\\ (t-4)^2&= \frac{44}{2} \\ t-4& = \pm\sqrt{22}\\ t&= 4\pm \sqrt{22}. \end{aligned} $$ Find the two separate solutions: $$ \begin{aligned} t&= 4+ \sqrt{22} &\approx 8.69 \\ \textbf{or}\\ t&= 4- \sqrt{22}\\ & \approx -0.69.\ \end{aligned} $$ $x$-intercepts: $(-0.69,0), (8.69, 0)$. Step 4: Find the domain and range of the function and sketch it. Domain: All real numbers, Range: $[-44, \infty) $.
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