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: 96

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. $$ \begin{aligned} k(p) &=5(p-5)^2-105. \end{aligned} $$ Step 1: We first determine the direction in which the function opens: The given function opens upward because the constant $a= 5$ is positive. Step 2: Determine the vertex and the equation for the axis of symmetry. The vertex is $(5,-105)$ and the equation for the axis of symmetry is $x = 5$. 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 $x$. $$ \begin{aligned} k(0)& =5(0-5)^2-105\\ &= 20\\ &\text{y-intercept: (0,20)}. \end{aligned} $$ Set $ y = 0$ and solve. $$ \begin{aligned} 5(p-5)^2-105& =0\\ (p-5)^2&= \frac{105}{5} \\ p-5& = \pm\sqrt{21}\\ p&= 5\pm \sqrt{21}. \end{aligned} $$ Find the two separate solutions: $$ \begin{aligned} p&= 5+ \sqrt{21}\\ &\approx 9.58 \\ \textbf{or}\\ p&= 5- \sqrt{21}\\ & \approx 0.42 \end{aligned} $$ $x$-intercepts: $(0.42,0), (9.58, 0)$. Step 4: Find the domain and range of the function and sketch it. Domain: All real numbers, Range: $[-105, \infty) $.
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