Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 8 - Review Exercises - Page 575: 43

Answer

Vertex: $\left(-4,-3\right)$ Axis of Symmetry: $y=-3$ Domain: $\{x|x\ge-4\}$ Range: set of all real numbers Graph of $x=2(y+3)^2-4$

Work Step by Step

Since the vertex of the equation $ x=a(y-k)^2+h $ is given by $(h,k)$, then the vertex of the quadratic equation, $ x=2(y+3)^2-4 $, is $ \left(-4,-3\right) $. The axis of symmetry of the equation $x=a(y-k)^2+h$ is given by $y=k$. With $k= -3 $ then the axis of symmetry is $ y=-3 $. To graph the parabola, find points that are on the parabola. This can be done by substituting values of $y$ and solving the corresponding value of $x$. That is \begin{array}{l|r} \text{If }y=-5: & \text{If }y=-4: \\\\ x=2(-5+3)^2-4 & x=2(-4+3)^2-4 \\ x=2(-2)^2-4 & x=2(-1)^2-4 \\ x=2(4)-4 & x=2(1)-4 \\ x=8-4 & x=2-4 \\ x=4 & x=-2 .\end{array} Hence, the points $ (4,-5) $ and $ (-2,-4) $ are on the parabola. Reflecting these points about the axis of symmetry, the points $ (-2,-2) $ and $ (4,-1) $ are also on the parabola. Using the points $\{ (4,-5), (-2,-4), \left(-4,-3\right), (-2,-2), (4,-1) \}$ the graph of the parabola is determined (see graph above). Using the graph, the domain (values of $x$ used in the graph) is $ \{x|x\ge-4\} $. The range (values of $y$ used in the graph) is the set of all real numbers.
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