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

find_the_fun
Messages
147
Reaction score
0
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.
 
Physics news on Phys.org
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
 

Similar threads

Replies
5
Views
2K
Replies
3
Views
2K
Replies
2
Views
2K
Replies
14
Views
2K
Replies
5
Views
4K
Replies
4
Views
3K
Back
Top