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 626: 22

Answer

$f(x)=e^{x^2/2}+1$

Work Step by Step

Let $y=f(x)$. The differential equation would be $y'=xy-x$. Find the general solution: $\frac{dy}{dx}=xy-x$ $\frac{dy}{dx}=x(y-1)$ (Separate the variables) $\frac{1}{y-1}dy=xdx$ (Integrate) $\int \frac{1}{y-1}dy=\int x dx$ $\ln (y-1)=\frac{x^2}{2}+C$ Find the value of $C$ by substituting $y(0)=2$: $\ln (2-1)=\frac{0^2}{2}+C$ $\ln 1=\frac{0}{2}+C$ $0=0+C$ $C=0$ So, $\ln (y-1)=\frac{x^2}{2}$ Taking the exponent, $y-1=e^{x^2/2}$ $y=e^{x^2/2}+1$ Thus, the solution is $f(x)=e^{x^2/2}+1$.
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