Finite Math and Applied Calculus (6th Edition)

Published by Brooks Cole
ISBN 10: 1133607705
ISBN 13: 978-1-13360-770-0

Chapter 10 - Section 10.3 - Limits and Continuity: Algebraic Viewpoint - Exercises - Page 718: 37

Answer

12

Work Step by Step

1. f is a closed function (we know by Th.10.1 that it is continuous), that is, L= $\displaystyle \lim_{x\rightarrow a}f(x)$ = $f(a)$, for all a from the domain of f. 2. evaluating: $f(2)$, (plugging $x=2$) results in an indeterminate form 0/0. So, we see that $x=2$ is NOT in the domain of f. We apply case 2 (of step 2). Simplifying $f(x)$, $\displaystyle \frac{x^{3}-8}{x -2}=\frac{x^{3}-2^3}{x -2}=$... difference of cubes... $=\displaystyle \frac{(x-2)(x^{2}+2x+4)}{(x-2)}=$...reduce...$=x^{2}+2x+4=g(x)$ $g(2)=2^{2}+2(2)+4=12$ ($2$ is in the domain of g, g is closed-form), so $\displaystyle \lim_{x\rightarrow 2}f(x)=\lim_{x\rightarrow 2}g(x)=g(2)=12$
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