Solving Bernoulli's Equation: Step-by-Step Guide

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SUMMARY

The discussion focuses on solving the differential equation represented by the homework statement, specifically the equation 2xy' + y^3e^(-2x) = 2xy. The solution involves transforming the equation into a standard form using the integrating factor method, where P(x) = -1 and Q(x) = -e^(-2x)/2x. The substitution v = y^(1-n) is utilized, leading to the equation dv/dx + 2v = e^(-2x)/x, which requires integration to find the solution.

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domesticbark
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Homework Statement


[itex] 2xy'+y^3e^(-2x)=2xy[/itex]



Homework Equations


[itex] dy/dx + P(x)y=Q(x)y^n[/itex]
[itex] v=y^(1-n)[/itex]



The Attempt at a Solution


[itex] dy/dx-y=-y^3e^(-2x)/2x[/itex]

[itex] P(x)=-1<br /> Q(x)=-e^(-2x)/2x[/itex]

[itex] n=3[/itex]
[itex] v=1/y^2[/itex]

[itex] dy/dx=dy/dv*dv/dx[/itex]

[itex] dy/dx=-1/2v^-(3/2)*dv/dx[/itex]

[itex] -1/2v^(-3/2)*dv/dx-v^(-1/2)=-v^(-3/2)e^(-2x)/2x[/itex]

[itex] dv/dx + 2v=e^(-2x)/x[/itex]

[itex] e^(\int P(x)\,dx)=e^(\int -1\,dx)=e^(-x)[/itex]

[itex] dv/dx*e^(-x)+2ve^(-x)=e^(-3x)/x[/itex]


This is supposed to look live reverse chain rule so I get [itex](e^(-x)*v)'=e^(-3x)/x[/itex]
but it doesn't look right and I have no idea how to do the integral required to then solve the rest of this problem.
 
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domesticbark said:

Homework Statement


[itex] 2xy'+y^3e^(-2x)=2xy[/itex]

Homework Equations


[itex] dy/dx + P(x)y=Q(x)y^n[/itex]
[itex] v=y^(1-n)[/itex]

The Attempt at a Solution


[itex] dy/dx-y=-y^3e^(-2x)/2x[/itex]

That should be ##\frac{dy}{dx}-y = -y^3e^{-2x}##
 

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