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: 94

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. $$ \begin{aligned} m(d) &= 4(d+3)^2-66. \end{aligned} $$ Step 1: We first determine the direction in which the function opens: The given function opens upward because the constant $a= 4$ is positive. Step 2: Determine the vertex and the equation for the axis of symmetry. The vertex is $(-3,-66)$ and the equation for the axis of symmetry is $x = -3$. 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 $x$. $$ \begin{aligned} m(0)& =4(0+3)^2-66\\ &= -30\\ &\textbf{y-intercept: (0,-30)}. \end{aligned} $$ Set $ y = 0$ and solve. $$ \begin{aligned} 4(d+3)^2-66 & =0\\ (d+3)^2&= \frac{66}{4} \\ d+3& = \pm\sqrt{16.5}\\ d&= -3\pm \sqrt{16.5}. \end{aligned} $$ Find the two separate solutions: $$ \begin{aligned} d&= -3+ \sqrt{16.5}\approx 1.062 \\ \textbf{or}\\ d&= -3-\sqrt{16.5}\approx = -7.062 \\ &\textbf{x-intercepts: (-7.062,0), (1.062, 0)}. \end{aligned} $$ Step 4: Find the domain and range of the function and sketch it. Domain: All real numbers, Range: $[-66, \infty) $.
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