Calculus with Applications (10th Edition)

Published by Pearson
ISBN 10: 0321749006
ISBN 13: 978-0-32174-900-0

Chapter 10 - Differential Equations - 10.1 Solutions of Elementary and Separable Differential Equations - 10.1 Exercises - Page 535: 18

Answer

$$y = {x^4} - {x^3} + \frac{{{x^2}}}{2} - \frac{1}{2}$$

Work Step by Step

$$\eqalign{ & \frac{{dy}}{{dx}} = 4{x^3} - 3{x^2} + x;\,\,\,\,\,\,\,y\left( 1 \right) = 0 \cr & {\text{Separating variables leads to}} \cr & dy = \left( {4{x^3} - 3{x^2} + x} \right)dx \cr & {\text{To solve this equation}}{\text{, determine the antiderivative of each side}} \cr & \int {dy} = \int {\left( {4{x^3} - 3{x^2} + x} \right)dx} \cr & {\text{integrating by using the power rule }} \cr & y = 4\left( {\frac{{{x^4}}}{4}} \right) - 3\left( {\frac{{{x^3}}}{3}} \right) + \frac{{{x^2}}}{2} + C \cr & y = {x^4} - {x^3} + \frac{{{x^2}}}{2} + C\,\,\,\,\,\left( {\bf{1}} \right) \cr & \cr & {\text{We can find the constant }}C{\text{ using the initial value problem}}\,\,y\left( 1 \right) = 0 \cr & y\left( 1 \right) = 0{\text{ implies that }}y = 0{\text{ when }}x = 1 \cr & {\text{Substituting these values into }}\left( {\bf{1}} \right) \cr & 0 = {\left( 1 \right)^4} - {\left( 1 \right)^3} + \frac{{{{\left( 1 \right)}^2}}}{2} + C \cr & 0 = \frac{1}{2} + C \cr & C = - \frac{1}{2} \cr & {\text{Substitute }}C = - \frac{1}{2}{\text{ into }}\left( {\bf{1}} \right){\text{ to find the particular solution}} \cr & y = {x^4} - {x^3} + \frac{{{x^2}}}{2} - \frac{1}{2} \cr} $$
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