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 2 - First Order Differential Equations - 2.1 Linear Equations; Method of Integrating Factors - Problems - Page 39: 7

Answer

$y = (t^2 + C)e^{-t^2}$

Work Step by Step

$$y' + 2ty = 2te^{-t^2}$$ We solve this by the integrating factor method: $$\mu(t) = e^{\int P(t),dt}$$ Here, (P(t) = 2t). Therefore, $$\mu(t) = e^{\int 2t,dt} = e^{t^2}$$ Now, multiplying both sides of the equation by (\mu(t)): $$e^{t^2}(y' + 2ty) = e^{t^2} \cdot 2te^{-t^2}$$ $$e^{t^2}y' + 2te^{t^2}y = 2t$$ Notice the left-hand side of the equation: $$(e^{t^2}y)' = 2t$$ Then, integrating both sides: $$\int (e^{t^2}y)',dt = \int 2t,dt$$ $$e^{t^2}y = t^2 + C$$ Dividing both sides by (e^{t^2}): $$y = (t^2 + C)e^{-t^2}$$
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