College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 3 - Section 3.5 - Graphing Techniques: Transformations - 3.5 Assess Your Underdstanding - Page 257: 13


Option $(L)$

Work Step by Step

RECALL: (i) $y=-f(x)$ involves a reflection about the x-axis of the parent function $y=f(x)$. (ii) $y=af(x)$ involves either a vertical compression by a factor of $a$ of the parent function $f(x)$ when $a\gt 1$or a vertical stretch if $0\lt a \lt1$. (iii) $y=f(x) + k$ involves either a vertical shift of $k$ units upward of the parent function when $k\gt 0$ or $|k|$ units downward when $k \lt0$. The graph involves an inverted V-shape, so its parent function is $y=|x|$. Note that compared to the parent function's graph, whose vertex is at $(0, 0)$, opens upward, and contains the point $(1, 1)$, the given graph opens downward, has its vertex at $(0, 0)$, and contains the point $(1, -2)$. This implies that the given graph involves the following transformations of the parent function $f(x)=|x|$: (1) a reflection about the x-axis. This means the tentative equation of the graph is $y=-|x|$. (2) a vertical compression by a factor of $2$ (since instead of containing $(1, -1)$ after the reflection about the x-axis, the graph contains $(1, -2)$ instead. Thus, the equation of the graph is $y=-2|x|$. Therefore, the answer is Option $(L)$.
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