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

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SUMMARY

The discussion focuses on solving the differential equation (DE) \(\frac{dy}{dx} = e^{3x+2y}\) using the method of separation of variables. The equation is manipulated to isolate variables, resulting in \(\frac{1}{e^{2y}} dy = e^{3x} dx\). After integrating both sides, the expression simplifies to \(e^{-2y} = -\frac{2}{3}e^{3x} - 2C\). The final step involves taking the natural logarithm of both sides to isolate \(y\), which is crucial for solving the DE.

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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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