Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 3: Derivatives - Section 3.3 Differentiation Rules - Exercises 3.3 - Page 125: 39

Answer

$$\frac{{dp}}{{dq}} = \frac{1}{6}q + \frac{1}{{6{q^3}}} + \frac{1}{{{q^5}}}{\text{ and }}\frac{{{d^2}p}}{{d{q^2}}} = \frac{1}{6} - \frac{1}{{2{q^4}}} - \frac{5}{{{q^6}}}$$

Work Step by Step

$$\eqalign{ & p = \left( {\frac{{{q^2} + 3}}{{12q}}} \right)\left( {\frac{{{q^4} - 1}}{{{q^3}}}} \right) \cr & {\text{Use the distributive property}} \cr & p = \frac{{\left( {{q^2} + 3} \right)\left( {{q^4} - 1} \right)}}{{12q\left( {{q^3}} \right)}} \cr & p = \frac{{{q^6} - {q^2} + 3{q^4} - 3}}{{12{q^4}}} \cr & p = \frac{{{q^6}}}{{12{q^4}}} - \frac{{{q^2}}}{{12{q^4}}} + \frac{{3{q^4}}}{{12{q^4}}} - \frac{3}{{12{q^4}}} \cr & p = \frac{{{q^2}}}{{12}} - \frac{1}{{12{q^2}}} + \frac{1}{4} - \frac{1}{{4{q^4}}} \cr & p = \frac{{{q^2}}}{{12}} - \frac{1}{{12}}{q^{ - 2}} + \frac{1}{4} - \frac{1}{4}{q^{ - 4}} \cr & \cr & {\text{Find the first derivative}} \cr & \frac{{dp}}{{dq}} = \frac{d}{{dq}}\left[ {\frac{{{q^2}}}{{12}} - \frac{1}{{12}}{q^{ - 2}} + \frac{1}{4} - \frac{1}{4}{q^{ - 4}}} \right] \cr & {\text{use }}\frac{d}{{dq}}\left[ {{q^n}} \right] = n{q^{n - 1}}{\text{ and }}\frac{d}{{dq}}\left[ c \right] = 0,{\text{ }}c{\text{ is a constant}} \cr & \frac{{dp}}{{dq}} = \frac{1}{{12}}\left( {2q} \right) - \frac{1}{{12}}\left( { - 2{q^{ - 3}}} \right) + 0 - \frac{1}{4}\left( { - 4{q^{ - 5}}} \right) \cr & \frac{{dp}}{{dq}} = \frac{1}{6}q + \frac{1}{6}{q^{ - 3}} + {q^{ - 5}} \cr & \frac{{dp}}{{dq}} = \frac{1}{6}q + \frac{1}{{6{q^3}}} + \frac{1}{{{q^5}}} \cr & \cr & {\text{Find the second derivative}} \cr & \frac{{{d^2}p}}{{d{q^2}}} = \frac{d}{{dq}}\left[ {\frac{1}{6}q + \frac{1}{6}{q^{ - 3}} + {q^{ - 5}}} \right] \cr & {\text{use }}\frac{d}{{dq}}\left[ {{q^n}} \right] = n{q^{n - 1}}{\text{ and }}\frac{d}{{dq}}\left[ c \right] = 0,{\text{ }}c{\text{ is a constant}} \cr & \frac{{{d^2}p}}{{d{q^2}}} = \frac{1}{6}\left( 1 \right) + \frac{1}{6}\left( { - 3{q^{ - 4}}} \right) - 5{q^{ - 6}} \cr & \frac{{{d^2}p}}{{d{q^2}}} = \frac{1}{6} - \frac{1}{2}{q^{ - 4}} - 5{q^{ - 6}} \cr & \frac{{{d^2}p}}{{d{q^2}}} = \frac{1}{6} - \frac{1}{{2{q^4}}} - \frac{5}{{{q^6}}} \cr} $$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.