Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 1 - First-Order Differential Equations - 1.6 First-Order Linear Differential Equations - Problems - Page 59: 10

Answer

\[x(t)=\frac{C+4e^t(t-1)}{t^2}\]

Work Step by Step

$t\large\frac{dx}{dt}+\small 2x=4e^t$ _____(1) $\large\frac{dx}{dt}+\large\frac{2}{t}\small x=\large\frac{4e^t}{t}$ ___(2) (1) is linear differential equation, Integrating factor:- $I(t)=e^{\int\large\frac{2}{t}}dt=e^{2\ln t}=t^2$ Multiply (2) by $I(t)$ \[t^2\frac{dx}{dt}+2xt=4e^tt\] \[\frac{d}{dt}[xt^2]=4te^t\] Integrating, \[xt^2=4\int te^tdt+C\] $C$ is constant of integration \[xt^2=4e^t(t-1)+C\] \[x(t)=\frac{C+4e^t(t-1)}{t^2}\] Hence general solution of (1) is $x(t)=\frac{C+4e^t(t-1)}{t^2}$
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