University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 2 - Section 2.2 - Limit of a Function and Limit Laws - Exercises - Page 68: 72

Answer

$$\lim_{x\to-2}F(x)=-1$$

Work Step by Step

$$F(x)=\frac{x^2+3x+2}{2-|x|}$$ (a) The table is shown below. As we can see from 2 tables below, as $x$ gets more decimals and approaches $-2$, the value of $F(x)$ also gets more decimals and apparently approaches $-1$. So I would estimate here that $\lim_{x\to-2}F(x)=-1$. (b) The graph is shown below. Again, looking at the graph, the closer $x$ approaches $-2$, the closer $F(x)$ gets to $-1$. (c) $$\lim_{x\to-2}F(x)=\lim_{x\to-2}\frac{x^2+3x+2}{2-|x|}$$ For $x\ge0$, $|x|=x$ and for $x\lt0$, $|x|=-x$ However, here we need to calculate the limit of $F(x)$ as $x\to-2$, and we care only the values of $x$ very close around $-2$, which is below $0$. So we can say here that we choose $x\lt0$, and $|x|=-x$ $$\lim_{x\to-2}F(x)=\lim_{x\to-2}\frac{x^2+3x+2}{2-(-x)}=\lim_{x\to-2}\frac{(x+1)(x+2)}{2+x}$$ $$\lim_{x\to-2}F(x)=\lim_{x\to-2}(x+1)=-2+1=-1$$ Therefore, $$\lim_{x\to-2}F(x)=-1$$
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