Finite Math and Applied Calculus (6th Edition)

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

Chapter 12 - Section 12.1 - Maxima and Minima - Exercises - Page 876: 16

Answer

$$\eqalign{ & \left( { - 2, - 1} \right),{\text{ Absolute minimum }} \cr & \left( { - 1,7} \right),{\text{ Absolute maximum }} \cr & \left( {1, - 1} \right){\text{, Absolute minimum }} \cr & \left( {2,7} \right),{\text{ Absolute maximum }} \cr} $$

Work Step by Step

$$\eqalign{ & g\left( x \right) = 2{x^3} - 6x + 3{\text{ with domain }}\left[ { - 2,2} \right] \cr & {\text{Differentiate}} \cr & g'\left( x \right) = \frac{d}{{dx}}\left[ {2{x^3} - 6x + 3} \right] \cr & g'\left( x \right) = 6{x^2} - 6 \cr & {\text{Find the stationary points}}{\text{, set }}g'\left( x \right) = 0 \cr & g'\left( x \right) = 6{x^2} - 6 \cr & 6{x^2} - 6 = 0 \cr & 6{x^2} = 6 \cr & x = \pm 1 \cr & {\text{There are no singular points}}{\text{, the derivative is defined for every }}x \cr & {\text{The domain of the function is }}\left[ { - 2,2} \right],{\text{ }} \cr & {\text{The endpoints are: }}x = - 2,{\text{ and }}x = 2 \cr & g\left( { - 2} \right) = 2{\left( { - 2} \right)^3} - 6\left( { - 2} \right) + 3 = - 1,{\text{ }}\left( { - 2, - 1} \right),{\text{ }}\left( {{\text{endpoint}}} \right) \cr & g\left( { - 1} \right) = 2{\left( { - 1} \right)^3} - 6\left( { - 1} \right) + 3 = 7,{\text{ }}\left( { - 1,7} \right){\text{, }}\left( {{\text{stationary point}}} \right) \cr & g\left( 1 \right) = 2{\left( 1 \right)^3} - 6\left( 1 \right) + 3 = - 1,{\text{ }}\left( {1, - 1} \right){\text{, }}\left( {{\text{stationary point}}} \right) \cr & g\left( 2 \right) = 2{\left( 2 \right)^3} - 6\left( 2 \right) + 3 = 7,{\text{ }}\left( {2,7} \right){\text{, }}\left( {{\text{endpoint}}} \right) \cr & {\text{Thus}},{\text{ we have found the following extrema:}} \cr & \left( { - 2, - 1} \right),{\text{ Absolute minimum }}\left( {{\text{endpoint}}} \right) \cr & \left( { - 1,7} \right),{\text{ Absolute maximum }}\left( {{\text{Stationary point}}} \right) \cr & \left( {1, - 1} \right){\text{, Absolute minimum }}\left( {{\text{Stationary point}}} \right) \cr & \left( {2,7} \right),{\text{ Absolute maximum }}\left( {{\text{endpoint}}} \right) \cr} $$
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