Differential equation Euler substitutio I was trying to solve this differential equation but can't figure out the final integral I get by variable separable method The equation is x^3 y' = y^3 + y^2 sqrt(y^2-x^2)

Wyatt Weeks

Wyatt Weeks

Answered question

2022-10-25

Differential equation Euler substitution
I was trying to solve this differential equation but can't figure out the final integral I get by variable separable method
The equation is
x 3 y = y 3 + y 2 y 2 x 2
I got the integral
d v v 3 + v 2 ( v 2 1 ) v
but can't figure out how to solve it.
The Euler substitution v = u 2 + 1 2 u could work but I can't seem to proceed with it.
Any help with this problem is much appreciated.

Answer & Explanation

Ramiro Sosa

Ramiro Sosa

Beginner2022-10-26Added 13 answers

Simply use a partial fraction decomposition to obtain:
d x x 3 + x 2 x 2 1 x = x 2 1 2 ( x 1 ) x 2 1 2 ( x + 1 ) 1 x d x
Use u substitute with x−1 and x+1 since x 2 1 = ( x + 1 ) ( x 1 ). I think that should do it.
Eliza Gregory

Eliza Gregory

Beginner2022-10-27Added 3 answers

I think I see a really fast answer to this. Divide numerator and denominator by v 3
v 3 d v 1 v 2 + 1 v 2 = v 3 d v ( 1 v 2 + 1 ) 1 v 2
t = 1 v 2 + 1 , d t = 2 v 3 d v 2 1 v 2 = v 3 d v 1 v 2
This drastically reduces the integral to d t t

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