Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 8 - Review Exercises - Page 658: 34

Answer

Vertex: $(-4,-2)$ $x$-intercepts: $-4-\sqrt 2,-4+\sqrt 2$ $y$-intercept: $14$

Work Step by Step

The function is in vertex form $f(x)=a(x-h)^2+k$: $$f(x)=(x+4)^2-2.$$ Identify the constants $a$, $h$, $k$: $$\begin{align*} a&=1\\ h&=-4\\ k&=-2. \end{align*}$$ Determine the vertex of the function: $$(h,k)=(-4,-2).$$ The axis of symmetry is $x=-4$. It opens upward because $a>0$. Determine the $x$-intercepts by solving the equation $f(x)=0$: $$\begin{align*} (x+4)^2-2&=0\\ (x+4)^2&=2\\ x+4&=\pm \sqrt 2\\ x+4=-\sqrt 2&\text{ or }x+4=\sqrt 2\\ x=-4-\sqrt 2&\text{ or }x=-4+\sqrt 2. \end{align*}$$ The $x$-intercepts are $-4-\sqrt 2$ and $-4+\sqrt 2$. Determine the $y$-intercept: $$f(0)=(0+4)^2-2=14.$$ The $y$-intercept is $14$. We plot the vertex $(-4,-2)$ and the intercept points $(-4-\sqrt 2,0)$, $(-4+\sqrt 2,0)$ and $(0,14)$, then join them to sketch the graph of the function:
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