Elementary Differential Equations and Boundary Value Problems 9th Edition

Published by Wiley
ISBN 10: 0-47038-334-8
ISBN 13: 978-0-47038-334-6

Chapter 3 - Second Order Linear Equations - 3.1 Homogenous Equations with Constant Coefficients - Problems - Page 144: 12

Answer

$${y}=-1-\exp^{-3x}$$

Work Step by Step

$$y''+3y'=0,\quad{y}(0)=-2,\quad{y'}(0)=3$$Let $y=e^{\lambda{x}}$ so that $(\ln{y})'=\lambda$. $${\lambda}^2+3{\lambda}=0$$ $$\lambda(\lambda+3)=0$$ $$\lambda_{1,2}=0,-3$$ The general solution is ${y}=c_{1}+c_{2}\exp^{-3x}$. Substituting in the constraints, we obtain $c_{1}+c_{2}=-2$ and $-3c_{2}=3\Rightarrow{c}_{2}=-1=c_{1}$. $$\therefore{y}=-1-\exp^{-3x}$$
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