Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 9 - Section 9.5 - Linear Equations - 9.5 Exercises - Page 625: 9

Answer

$y = \frac{2}{3}~\sqrt{x}+\frac{C}{x}$

Work Step by Step

A first-order linear differential equation is one that can be put into the form: $\frac{dy}{dx} + P(x)~y = Q(x)$ We can consider the given equation: $xy' + y = \sqrt{x}$ $y' +(\frac{1}{x})~y = \frac{\sqrt{x}}{x}$ Let $P(x) = \frac{1}{x}$ Let $Q(x) = \frac{\sqrt{x}}{x}$ We can find the integrating factor: $I(x) = e^{\int \frac{1}{x} ~dx} = e^{ln(x)} = x$ We can multiply by the integrating factor: $x~y'+y = \sqrt{x}$ $\frac{d}{dx}(x~y) = \sqrt{x}$ We can integrate both sides of the equation: $x~y = \int \sqrt{x}~dx$ $x~y = \frac{2}{3}~x^{3/2}+C$ $y = \frac{2}{3}~\sqrt{x}+\frac{C}{x}$
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