Calculus: Early Transcendentals 9th Edition

Published by Cengage Learning
ISBN 10: 1337613924
ISBN 13: 978-1-33761-392-7

Chapter 9 - Section 9.3 - Separable Equations - 9.3 Exercises - Page 627: 36

Answer

$y^2-2\ln x=4$

Work Step by Step

Find the initial condition: $y(1)=2+\int_1^1\frac{dt}{ty(t)}$ $y(1)=2+0$ $y(1)=2$ Construct a differential equation by differentiating the integral equation: $\frac{d}{dx}(y(x))=\frac{d}{dx}(2+\int_1^x\frac{dt}{ty(t)})$ $\frac{dy}{dx}=0+\frac{1}{xy(x)}$ $\frac{dy}{dx}=\frac{1}{xy}$ Solve for $y$ by separating variables: $y dy=\frac{1}{x}dx$ $\int y dy=\int \frac{1}{x}dx$ $\frac{y^2}{2}=\ln x+C$ Substitute the initial condition: $\frac{2^2}{2}=\ln 1+C$ $2=0+C$ $C=2$ We have now: $\frac{y^2}{2}=\ln x+2$ $y^2=2\ln x+4$ $y^2-2\ln x=4$ Thus, the solution is $y^2-2\ln x=4$.
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