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: 74

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. $$ \begin{aligned} f(x)=(x+6)^2-11. \end{aligned} $$ 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 $(-6,-11)$ and the equation for the axis of symmetry is $x = -6$. 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 $x$. $$ \begin{aligned} f(0) & =(0+6)^2-11 \\ & =36-11 \\ & =25. \end{aligned} $$ $y$-intercept: $(0,25)$ Set $ y = 0$ and solve.$$ \begin{aligned} (x+6)^2-11 & =0 \\ (x+6)^2 & =11 \\ x+6 & = \pm \sqrt{11} \\ x & =-6 \pm \sqrt{11}. \end{aligned} $$ Find the two separate solutions: $$ \begin{aligned} x & =-6+\sqrt{11}\approx =-2.68\\ x & =-6-\sqrt{11}\approx =-9.32. \end{aligned} $$ $x$-intercepts: $(-9.32,0), (-2.68 , 0)$. Step 4: Find the domain and range of the function and sketch it. Domain: All real numbers Range: $[-11, \infty) $.
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