Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 8 - Integration Techniques, L'Hopital's Rule, and Improper Integrals - 8.7 Exercises - Page 564: 57

Answer

$$ - \frac{3}{2}$$

Work Step by Step

$$\eqalign{ & \mathop {\lim }\limits_{x \to {2^ + }} \left[ {\frac{8}{{{x^2} - 4}} - \frac{x}{{x - 2}}} \right] \cr & {\text{Evaluate the limit}} \cr & \mathop {\lim }\limits_{x \to {2^ + }} \left[ {\frac{8}{{{x^2} - 4}} - \frac{x}{{x - 2}}} \right] = \frac{8}{{{2^2} - 4}} - \frac{2}{{2 - 2}} = \infty - \infty \cr & {\text{Simplify}} \cr & = \mathop {\lim }\limits_{x \to {2^ + }} \left[ {\frac{8}{{\left( {x + 2} \right)\left( {x - 2} \right)}} - \frac{x}{{x - 2}}} \right] \cr & = \mathop {\lim }\limits_{x \to {2^ + }} \left[ {\frac{{8 - x\left( {x + 2} \right)}}{{\left( {x + 2} \right)\left( {x - 2} \right)}}} \right] \cr & = \mathop {\lim }\limits_{x \to {2^ + }} \left[ {\frac{{8 - {x^2} - 2x}}{{\left( {x + 2} \right)\left( {x - 2} \right)}}} \right] \cr & = - \mathop {\lim }\limits_{x \to {2^ + }} \left[ {\frac{{{x^2} + 2x - 8}}{{\left( {x + 2} \right)\left( {x - 2} \right)}}} \right] \cr & {\text{Factor}} \cr & = - \mathop {\lim }\limits_{x \to {2^ + }} \left[ {\frac{{\left( {x + 4} \right)\left( {x - 2} \right)}}{{\left( {x + 2} \right)\left( {x - 2} \right)}}} \right] \cr & = - \mathop {\lim }\limits_{x \to {2^ + }} \left[ {\frac{{x + 4}}{{x + 2}}} \right] \cr & {\text{Evaluate the limit}} \cr & {\text{ = }} - \frac{{2 + 4}}{{2 + 2}} \cr & {\text{ = }} - \frac{3}{2} \cr} $$
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