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: 1

Answer

$$ y=c e^{-3 t}+(t / 3)-(1 / 9)+e^{-2 t} $$

Work Step by Step

\( \mathrm{W}^{\prime}+3 \mathrm{y}=\mathrm{t}+\mathrm{e}^{2} \) We solve this by the integrating factor method: \( \mu(t)=e^{k(x) d t} \) Here, \( \mathrm{p}(\mathrm{t})=3 \) Therefore, \( \mu(t)=e^{p_{t}} \) \( \mu(t)=e^{x} \) Now, multiplying both sides of the equation by \( \mu(t) \) : \( e^{x}\left(y^{\prime}+3 y\right)=e^{x}\left(t+e^{z}\right) \) \( e^{x y}+3 e^{x y}=e^{x} t+e^{x} e^{-x} \) \( e^{2} y^{\prime}+3 e^{x y}=e^{x} t+e^{t} \) Notice the left hand side of the equation: \( e^{x} y^{\prime}+3 e^{x} y=\left(e^{x} y\right)^{\prime} \) Therefore, the equation can be written as: \( \left(e^{2} y\right)^{\prime}=e^{x} t+e^{i} \) Then, integrating on both sides: \( \int\left(e^{x} y\right)^{\prime} d t=\int\left(e^{x} t+e^{i}\right) d t \) \( \mathrm{e}^{\mathrm{x}} \mathrm{y}=\int \mathrm{e}^{\mathrm{x}} \mathrm{d} \mathrm{d}+\int \mathrm{e} \mathrm{d} \mathrm{t} \) On the right hand side: \( \int e^{2} t d t=\left(t e^{x} / 3\right)-\left(e^{x} / 9\right) \) (by using \( \int u v^{\prime}=u v-\int u^{\prime} v, \) where \( u=t \) and \( \left.v^{\prime}=e^{x}\right) \) And, \intedt = e Therefore: (c here is the integrating constant) Dividing both sides with ex: \( y=(t / 3)-(1 / 9)+e^{i x}+c e^{x} \) The answer is: \( y=c e^{-s+}(t / 3)-(1 / 9)+e^{-z} \)
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.