MHB Separation of variables, can't get y out of exponent

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The discussion focuses on solving the differential equation \(\frac{dy}{dx} = e^{3x+2y}\) using separation of variables. The equation is separated into \(\frac{1}{e^{2y}} dy = e^{3x} dx\) and both sides are integrated, leading to \(\frac{-e^{2y}}{2} = \frac{e^{3x}}{3} + C\). A participant expresses difficulty in isolating \(y\) from the exponent. Another contributor suggests taking the natural logarithm of both sides after simplification, noting that the solution does not simplify further without specific boundary conditions. The conversation emphasizes the importance of careful manipulation and integration in solving differential equations.
find_the_fun
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Solve the DE by using separation of variables
[math]\frac{dy}{dx} = e^{3x+2y}[/math]

Break up [math]e^{3x+2y} = e^{3x}e^{2y}[/math] Move x's and y's to their own side of the equation.
[math]\frac{1}{e^{2y}} dy = e^{3x} dx[/math]
Integrate both sides of the equation to get [math]\frac{-e^{2y}}{2x}=\frac{e^{3x}}{3}+C[/math]

I don't know how to isolate the y; I don't know how to get it down from the exponent.
 
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find_the_fun said:
Solve the DE by using separation of variables
[math]\frac{dy}{dx} = e^{3x+2y}[/math]

Break up [math]e^{3x+2y} = e^{3x}e^{2y}[/math] Move x's and y's to their own side of the equation.
[math]\frac{1}{e^{2y}} dy = e^{3x} dx[/math]
Integrate both sides of the equation to get [math]\frac{-e^{2y}}{2x}=\frac{e^{3x}}{3}+C[/math]

I don't know how to isolate the y; I don't know how to get it down from the exponent.
I'm going to presume that the x on the LHS is a typo. Otherwise I have no idea where it came from.

Simplifying a bit we have:
[math]e^{-2y} = -\frac{2}{3}e^{3x} - 2C[/math]

Your turn: Take ln of both sides. And no, it doesn't simplify beyond this, unless C = 0, which is a matter for the boundary conditions, which you don't have.

-Dan
 

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