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Can someone help me with a differential equation?
Hello,
How can I find the general solution to this equation?
dy/dx = y^2(4 - y^2)
I have several in a similar format to solve. I'm a little stumped :(
Thank you Eric, I did actually get that far, but then I wasn't sure how to integrate it. I can't picture how to end up with y=something. :(
4 Answers
- 1 decade agoFavorite Answer
dy/dx = y^2(4-y^2)
dy/dx = 4y^2-y^4
dy * ( 1 / (4y^2-y^4) ) = dx
integrate both sides. Left side is not simple. I looked it up on wolframs integrals.com
(-y*log(y-2) - y * log(y+2) + 4 ) / (16* y) = x
solving for y looks difficult.
There might be a way using the something similar to the method of undetermined coefficients, but that is used for solving a linear differential equation.
- 1 decade ago
You can integrate 1/(y^2(4-y^2)) by partial fractions.
First factor the denomiator:
1/(y^2(2-y)(2+y)), then
solve for A, B C, and D:
(Ay+B)/y^2 + C/(2-y) + D/(2+y) = 1/(y^2(2-y)(2+y))
When you solve this, you get A=0, B=1/4, C=D=1/16.
This gives you three integrals that you can evaluate.