Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 11 - Section 11.1 - Finding Limits Using Tables and Graphs - Exercise Set - Page 1139: 31

Answer

a) $\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,f\left( x \right)=1$, since, as x approaches 2 from the left, the value of $ f\left( x \right)$ gets closer to the y-coordinate of 1. b) $\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,f\left( x \right)=2$, since, as x approaches 2 from the right, the value of $ f\left( x \right)$ gets closer to the y-coordinate of $2$. c) $\underset{x\to 2}{\mathop{\lim }}\,f\left( x \right)$, does not exist, because both the left hand and right-hand limits are unequal at $ x=2$. d) $ f\left( 2 \right)=2$, because this point $\left( 2,2 \right)$ is shown by the solid dot in the provided graph. e) $\underset{x\to {{2.5}^{-}}}{\mathop{\lim }}\,f\left( x \right)=2$, since, as x approaches 2.5 from the left, the value of $ f\left( x \right)$ gets closer to the y-coordinate of 2. f) $\underset{x\to {{2.5}^{+}}}{\mathop{\lim }}\,f\left( x \right)=2$, since, as x approaches 2.5 from the right, the value of $ f\left( x \right)$ gets closer to the y-coordinate of 2. g) $\underset{x\to 2.5}{\mathop{\lim }}\,f\left( x \right)=2$, because the left hand and right-hand limits at $ x=2.5$ are equal. h) $ f\left( 2.5 \right)=2$, because this point is shown by the solid dot in the provided graph.

Work Step by Step

(a) Consider the provided limit $\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,f\left( x \right)$. To find $\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,f\left( x \right)$, examine the portion of the graph near $ x=2$ but from the left. As x approaches 2 from the left, the value of $ f\left( x \right)$ gets closer to the y-coordinate of 1. This point $\left( 2,1 \right)$ is shown by the open dot in the above graph. The point $\left( 2,1 \right)$ has a y-coordinate of 1. Thus, $\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,f\left( x \right)=1$. Hence, the value of $\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,f\left( x \right)$ is 1. (b) Consider the provided limit $\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,f\left( x \right)$. To find $\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,f\left( x \right)$, examine the portion of the graph near $ x=2$ but from the right. As x approaches 2 from the right, the value of $ f\left( x \right)$ gets closer to the y-coordinate of $2$. This point $\left( 2,2 \right)$ is shown by the solid dot in the above graph. The point $\left( 2,2 \right)$ has a y-coordinate of $2$. Thus, $\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,f\left( x \right)=2$. Hence, the value of $\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,f\left( x \right)$ is $2$ . (c) Consider the provided limit $\underset{x\to 2}{\mathop{\lim }}\,f\left( x \right)$. To find $\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,f\left( x \right)$, examine the portion of the graph near $ x=2$ but from the right. As x approaches 2 from the right, the value of $ f\left( x \right)$ gets closer to the y-coordinate of $2$. This point $\left( 2,2 \right)$ is shown by the solid dot in the above graph. The point $\left( 2,2 \right)$ has a y-coordinate of $2$. Thus, $\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,f\left( x \right)=2$. Hence, the value of $\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,f\left( x \right)$ is $2$ . To find $\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,f\left( x \right)$, examine the portion of the graph near $ x=2$ but from the left. As x approaches 2 from the left, the value of $ f\left( x \right)$ gets closer to the y-coordinate of 1. This point $\left( 2,1 \right)$ is shown by the open dot in the above graph. The point $\left( 2,1 \right)$ has a y-coordinate of 1. Thus, $\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,f\left( x \right)=1$. Hence, the value of $\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,f\left( x \right)$ is 1. Since, $\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,f\left( x \right)=2$ and $\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,f\left( x \right)=1$. Here, both the left-hand limit and right-hand limit at $ x=2$ are unequal, Hence, $\underset{x\to 2}{\mathop{\lim }}\,f\left( x \right)$ does not exist. (d) Consider the provided function, $ f\left( 2 \right)$. To find $ f\left( 2 \right)$, examine the portion of the graph near $ x=2$. The graph of “f” at $ x=2$ is shown by the solid dot in the provided graph with coordinates $\left( 2,2 \right)$. Thus, $ f\left( 2 \right)=2$. (e) To find $\underset{x\to {{2.5}^{-}}}{\mathop{\lim }}\,f\left( x \right)$, examine the portion of the graph near $ x=2.5$ but from the left. As x approaches 2.5 from the left, the value of $ f\left( x \right)$ gets closer to the y-coordinate of 2. This point $\left( 2.5,2 \right)$ is on the parallel line shown at $ y=2$ in the above graph. The point $\left( 2.5,2 \right)$ has a y-coordinate of 2. Thus, $\underset{x\to {{2.5}^{-}}}{\mathop{\lim }}\,f\left( x \right)=2$. Hence, the value of $\underset{x\to {{2.5}^{-}}}{\mathop{\lim }}\,f\left( x \right)$ is 2. (f) Consider the provided limit $\underset{x\to {{2.5}^{+}}}{\mathop{\lim }}\,f\left( x \right)$. To find $\underset{x\to {{2.5}^{+}}}{\mathop{\lim }}\,f\left( x \right)$, examine the portion of the graph near $ x=2.5$ but from the right. As x approaches 2.5 from the right, the value of $ f\left( x \right)$ gets closer to the y-coordinate of 2. This point $\left( 2.5,2 \right)$ is on the parallel line shown at $ y=2$ in the above graph Thus $\underset{x\to {{2.5}^{+}}}{\mathop{\lim }}\,f\left( x \right)=2$. Hence, the value of $\underset{x\to {{2.5}^{+}}}{\mathop{\lim }}\,f\left( x \right)$ is 2. (g) Consider the provided limit $\underset{x\to 2.5}{\mathop{\lim }}\,f\left( x \right)$. To find $\underset{x\to {{2.5}^{+}}}{\mathop{\lim }}\,f\left( x \right)$, examine the portion of the graph near $ x=2.5$ but from the right. As x approaches 2.5 from the right, the value of $ f\left( x \right)$ gets closer to the y-coordinate of 2. This point $\left( 2.5,2 \right)$ is on the parallel line shown at $ y=2$ in the above graph Thus $\underset{x\to {{2.5}^{+}}}{\mathop{\lim }}\,f\left( x \right)=2$. Hence, the value of $\underset{x\to {{2.5}^{+}}}{\mathop{\lim }}\,f\left( x \right)$ is 2. To find $\underset{x\to {{2.5}^{-}}}{\mathop{\lim }}\,f\left( x \right)$, examine the portion of the graph near $ x=2.5$ but from the left. As x approaches 2.5 from the left, the value of $ f\left( x \right)$ gets closer to the y-coordinate of 2. This point $\left( 2.5,2 \right)$ is on the parallel line shown at $ y=2$ in the above graph. The point $\left( 2.5,2 \right)$ has a y-coordinate of 2. Thus, $\underset{x\to {{2.5}^{-}}}{\mathop{\lim }}\,f\left( x \right)=2$. Hence, the value of $\underset{x\to {{2.5}^{-}}}{\mathop{\lim }}\,f\left( x \right)$ is 2. Since, $\underset{x\to {{2.5}^{+}}}{\mathop{\lim }}\,f\left( x \right)=2$ and $\underset{x\to {{2.5}^{-}}}{\mathop{\lim }}\,f\left( x \right)=2$. Here, both the left-hand limit and right-hand limit at $ x=2.5$ are equal, Hence, $\underset{x\to 2.5}{\mathop{\lim }}\,f\left( x \right)=2$ . (h) Consider the provided function, $ f\left( 2.5 \right)$. To find $ f\left( 2.5 \right)$, examine the portion of the graph near $ x=2.5$. The graph of “f” at $ x=2.5$ is shown by the solid dot in the provided graph with coordinates $\left( 2.5,2 \right)$. Thus, the function $ f\left( 2.5 \right)=2$. .
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