Calculus Concepts: An Informal Approach to the Mathematics of Change 5th Edition

Published by Brooks Cole
ISBN 10: 1-43904-957-2
ISBN 13: 978-1-43904-957-0

Chapter 3 - Determining Change: Derivatives - 3.6 Activities - Page 237: 8

Answer

$$f'\left( x \right) = \frac{{10.8{x^3} + 90{x^2} - 8.1}}{{{{\left( {2.7x + 15} \right)}^2}}}$$

Work Step by Step

$$\eqalign{ & f\left( x \right) = \frac{{2{x^3} + 3}}{{2.7x + 15}} \cr & {\text{Calculate the derivative of the function}} \cr & f'\left( x \right) = \frac{d}{{dx}}\left( {\frac{{2{x^3} + 3}}{{2.7x + 15}}} \right) \cr & {\text{Use the quotient rule }}\left( {{\text{see the page 237}}} \right) \cr & f'\left( x \right) = \frac{{\left( {2.7x + 15} \right)\left( {2{x^3} + 3} \right)' - \left( {2{x^3} + 3} \right)\left( {2.7x + 15} \right)'}}{{{{\left( {2.7x + 15} \right)}^2}}} \cr & {\text{compute derivatives}} \cr & f'\left( x \right) = \frac{{\left( {2.7x + 15} \right)\left( {6{x^2}} \right) - \left( {2{x^3} + 3} \right)\left( {2.7} \right)}}{{{{\left( {2.7x + 15} \right)}^2}}} \cr & {\text{Multiplying}} \cr & f'\left( x \right) = \frac{{16.2{x^3} + 90{x^2} - 5.4{x^3} - 8.1}}{{{{\left( {2.7x + 15} \right)}^2}}} \cr & f'\left( x \right) = \frac{{10.8{x^3} + 90{x^2} - 8.1}}{{{{\left( {2.7x + 15} \right)}^2}}} \cr} $$
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