Finite Math and Applied Calculus (6th Edition)

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

Chapter 14 - Section 14.5 - Improper Integrals and Applications - Exercises - Page 1059: 17

Answer

$$\frac{5}{4}\left( {\root 5 \of {{3^4}} - 1} \right)$$

Work Step by Step

$$\eqalign{ & \int_{ - 2}^2 {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx \cr & {\text{The integrand }}\frac{3}{{{x^{1/3}}}}{\text{ is not continuous to }}x = - 1,{\text{ then}} \cr & {\text{Write the integral as}} \cr & \int_{ - 2}^2 {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx = \int_{ - 2}^{ - 1} {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx + \int_{ - 1}^2 {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx \cr & {\text{Improper Integral with an Infinite Limit of Integration}} \cr & \int_{ - 2}^2 {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx = \mathop {\lim }\limits_{a \to - {1^ - }} \int_{ - 2}^a {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx + \mathop {\lim }\limits_{b \to - {1^ + }} \int_b^2 {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx \cr & {\text{*Computing }}\mathop {\lim }\limits_{a \to - {1^ - }} \int_{ - 2}^a {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx \cr & \mathop {\lim }\limits_{a \to - {1^ - }} \int_{ - 2}^a {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx = \mathop {\lim }\limits_{a \to - {1^ - }} \left[ {\frac{5}{4}{{\left( {x + 1} \right)}^{4/5}}} \right]_{ - 2}^a \cr & = \mathop {\lim }\limits_{a \to - {1^ - }} \left[ {\frac{5}{4}{{\left( {a + 1} \right)}^{4/5}} - \frac{5}{4}{{\left( { - 2 + 1} \right)}^{4/5}}} \right] \cr & = \mathop {\lim }\limits_{a \to - {1^ - }} \left[ {\frac{5}{4}{{\left( {a + 1} \right)}^{4/5}} - \frac{5}{4}} \right] \cr & = \frac{5}{4}{\left( { - 1 + 1} \right)^{4/5}} - \frac{5}{4} \cr & = - \frac{5}{4} \cr & {\text{*Computing }}\mathop {\lim }\limits_{b \to - {1^ + }} \int_b^2 {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx \cr & \mathop {\lim }\limits_{b \to - {1^ + }} \int_b^2 {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx = \mathop {\lim }\limits_{b \to - {1^ + }} \left[ {\frac{5}{4}{{\left( {x + 1} \right)}^{4/5}}} \right]_b^2 \cr & = \mathop {\lim }\limits_{b \to - {1^ + }} \left[ {\frac{5}{4}{{\left( {2 + 1} \right)}^{4/5}} - \frac{5}{4}{{\left( {b + 1} \right)}^{4/5}}} \right] \cr & = \mathop {\lim }\limits_{b \to - {1^ + }} \left[ {\frac{5}{4}{{\left( 3 \right)}^{4/5}} - \frac{5}{4}{{\left( {b + 1} \right)}^{4/5}}} \right] \cr & = \frac{5}{4}{\left( 3 \right)^{4/5}} - \frac{5}{4}{\left( { - 1 + 1} \right)^{4/5}} \cr & = \frac{5}{4}{\left( 3 \right)^{4/5}} \cr & {\text{Therefore,}} \cr & \int_{ - 2}^2 {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx = - \frac{5}{4} + \frac{5}{4}{\left( 3 \right)^{4/5}} \cr & \int_{ - 2}^2 {\frac{1}{{{{\left( {x + 1} \right)}^{1/5}}}}} dx = \frac{5}{4}\left( {\root 5 \of {{3^4}} - 1} \right) \cr} $$
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