Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 4 - Applications of the Derivative - 4.8 Newton's Method - 4.8 Exercises - Page 316: 10

Answer

\[\boxed{\begin{array}{*{20}{c}} n&{{x_n}} \\ 0&{ - 2.000000} \\ 1&{ - 1.625000} \\ 2&{ - 1.485786} \\ 3&{ - 1.465956} \\ 4&{ - 1.465571} \\ 5&{ - 1.465571} \\ 6&{ - 1.465571} \\ 7&{ - 1.465571} \\ 8&{ - 1.465571} \\ 9&{ - 1.465571} \\ {10}&{ - 1.465571} \end{array}}\]

Work Step by Step

\[\begin{gathered} {\text{Let }}f\left( x \right) = {x^3} + {x^2} + 1,{\text{ and }}{x_0} = - 2 \hfill \\ {\text{Using the Newton's Method }}{x_{n + 1}} = {x_n} - \frac{{f\left( {{x_n}} \right)}}{{f'\left( {{x_n}} \right)}} \hfill \\ f'\left( x \right) = 3{x^2} + 2x \hfill \\ {\text{Then evaluating }}f\left( {{x_n}} \right){\text{ and }}f'\left( {{x_n}} \right) \hfill \\ {x_{n + 1}} = {x_n} - \frac{{x_n^3 + x_n^2 + 1}}{{3x_n^2 + 2{x_n}}} \hfill \\ \hfill \\ {\text{Taking }}{x_0} = - 2 \hfill \\ {x_0} = - 2 \hfill \\ {x_{0 + 1}} = {x_1} = - 2 - \frac{{{{\left( { - 2} \right)}^3} + {{\left( { - 2} \right)}^2} + 1}}{{3{{\left( { - 2} \right)}^2} + 2\left( { - 2} \right)}} = - 1.625000 \hfill \\ {x_{1 + 1}} = {x_2} = - 1.625000 - \frac{{{{\left( { - 1.625000} \right)}^3} + {{\left( { - 1.625000} \right)}^2} + 1}}{{3{{\left( { - 1.625000} \right)}^2} + 2\left( { - 1.625000} \right)}} \approx - 1.485786 \hfill \\ {x_{1 + 2}} = {x_3} = - 1.485786 - \frac{{{{\left( { - 1.485786} \right)}^3} + {{\left( { - 1.485786} \right)}^2} + 1}}{{3{{\left( { - 1.485786} \right)}^2} + 2\left( { - 1.485786} \right)}} \approx - 1.465956 \hfill \\ {x_{1 + 3}} = {x_4} = - 1.465956 - \frac{{{{\left( { - 1.465956} \right)}^3} + {{\left( { - 1.465956} \right)}^2} + 1}}{{3{{\left( { - 1.465956} \right)}^2} + 2\left( { - 1.465956} \right)}} \approx - 1.465571 \hfill \\ {x_{1 + 4}} = {x_5} = - 1.465571 - \frac{{{{\left( { - 1.465571} \right)}^3} + {{\left( { - 1.465571} \right)}^2} + 1}}{{3{{\left( { - 1.465571} \right)}^2} + 2\left( { - 1.465571} \right)}} \approx - 1.465571 \hfill \\ {x_{1 + 5}} = {x_6} = - 1.465571 - \frac{{{{\left( { - 1.465571} \right)}^3} + {{\left( { - 1.465571} \right)}^2} + 1}}{{3{{\left( { - 1.465571} \right)}^2} + 2\left( { - 1.465571} \right)}} \approx - 1.465571 \hfill \\ {x_{1 + 6}} = {x_7} = - 1.465571 - \frac{{{{\left( { - 1.465571} \right)}^3} + {{\left( { - 1.465571} \right)}^2} + 1}}{{3{{\left( { - 1.465571} \right)}^2} + 2\left( { - 1.465571} \right)}} \approx - 1.465571 \hfill \\ {x_{1 + 7}} = {x_8} = - 1.465571 - \frac{{{{\left( { - 1.465571} \right)}^3} + {{\left( { - 1.465571} \right)}^2} + 1}}{{3{{\left( { - 1.465571} \right)}^2} + 2\left( { - 1.465571} \right)}} \approx - 1.465571 \hfill \\ {x_{1 + 8}} = {x_9} = - 1.465571 - \frac{{{{\left( { - 1.465571} \right)}^3} + {{\left( { - 1.465571} \right)}^2} + 1}}{{3{{\left( { - 1.465571} \right)}^2} + 2\left( { - 1.465571} \right)}} \approx - 1.465571 \hfill \\ {x_{1 + 9}} = {x_{10}} = - 1.465571 - \frac{{{{\left( { - 1.465571} \right)}^3} + {{\left( { - 1.465571} \right)}^2} + 1}}{{3{{\left( { - 1.465571} \right)}^2} + 2\left( { - 1.465571} \right)}} \approx - 1.465571 \hfill \\ \hfill \\ {\text{Thus}}{\text{, we obtain}} \hfill \\ \boxed{\begin{array}{*{20}{c}} n&{{x_n}} \\ 0&{ - 2.000000} \\ 1&{ - 1.625000} \\ 2&{ - 1.485786} \\ 3&{ - 1.465956} \\ 4&{ - 1.465571} \\ 5&{ - 1.465571} \\ 6&{ - 1.465571} \\ 7&{ - 1.465571} \\ 8&{ - 1.465571} \\ 9&{ - 1.465571} \\ {10}&{ - 1.465571} \end{array}} \hfill \\ \end{gathered} \]
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