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 - 1.11 Some Higher-Order Differential Equations - Problems - Page 105: 4

Answer

$y(x)=(C_1e^x+C_2)^{\frac{1}{3}}$

Work Step by Step

We are given: $$y''+2y^{-1}(y')^2=y'$$ Suppose that $a= \dfrac{dy}{dx}$ and $ \dfrac{da}{dx}= \dfrac{d^2y}{dx^2}$ Integrating factor; $I.P.=e^{\int \frac{2}{y} dy}=e^{2 \ln y}=y^{2}$ Now, $\dfrac{d}{dx}(ay^{2})=y^2$ Integrate to obtain: $ay^{2}=y^3+C \implies dx=\frac{y^2dy}{y^3+C}$ Continue to integrate: $x+C_1=\frac{1}{3}\ln(y^3+C_2)$ $y^3=C_1e^x+C_2$ Therefore, the general solution is: $y(x)=(C_1e^x+C_2)^{\frac{1}{3}}$
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