Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 8 - Mathematical Modeling With Differential Equations - 8.1 Modeling With Differential Equations - Exercises Set 8.1 - Page 567: 26

Answer

$$y = \frac{{{e^x} + 1}}{x},{\text{ where }}x > 0$$

Work Step by Step

$$\eqalign{ & xy' + y = {e^x},{\text{ }}y\left( 1 \right) = 1 + e \cr & {\text{The left - hand side can be interpreted as the derivative of the}} \cr & {\text{product }}{x^2}y.{\text{ }}\frac{d}{{dx}}\left[ {xy} \right] = xy' + y = {e^x},{\text{ then,}} \cr & xy' + y = {e^x} \cr & \frac{d}{{dx}}\left[ {xy} \right] = {e^x} \cr & {\text{Integrate both sides with respect to }}x \cr & xy = {e^x} + C \cr & {\text{Solve for }}y \cr & y = \frac{{{e^x}}}{x} + \frac{C}{x} \cr & {\text{Use the initial condition }}y\left( 1 \right) = 1 + e \cr & 1 + e = \frac{{{e^1}}}{1} + \frac{C}{1} \cr & 1 + e = e + C \cr & C = 1 \cr & {\text{,then}} \cr & y = \frac{{{e^x}}}{x} + \frac{1}{x} \cr & y = \frac{{{e^x} + 1}}{x},{\text{ where }}x > 0 \cr} $$
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