Solve the differential equation 3 y <mspace width="thinmathspace" /> d x &#x2212

klipbodok6

klipbodok6

Answered question

2022-07-08

Solve the differential equation
3 y d x x ( 3 x n y sin y + 3 ) d y = 0.
I need to find the general solution for both n = 0 and n = 3. So, for n = 0 is done because the differential equation becomes a separable equation. However, I can't find a solution for n = 3 because it is not a Bernoulli equation nor an exact DE. If someone could help me, it would be great.

Answer & Explanation

Pranav Greer

Pranav Greer

Beginner2022-07-09Added 13 answers

3 y d x x ( 3 x n y sin y + 2 ) d y = 0           ( 1 )
Rewrite it as
x n 1 d x d y x n y = sin y         ( 2 )
Let x n = u, we get
d u d y n u y = n sin y         ( 3 )
This becomes a Linear ODE with Integrating factor as I = y n . Its solution for n = 3 can be written as
u ( x ) = 3 y 3 sin y   y 3 d y + C y 3
x 3 = 3 y 3 [ c o s ( 2 y ) y sin y 2 y 2 1 2 S i ( y ) ] + C y 3
Edit: Eq.(2) is known ad Bernoulli equation.

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