I need some hints for solving yy''-(y')^2=xy^2 I noticed that the

Halkadvalseln

Halkadvalseln

Answered question

2021-11-19

I need some hints for solving yy(y)2=xy2
I noticed that the left hand side is close to (yy):
yy(y)2=xy2yy+(y)22(y)2=xy2(yy)2(y)2=xy2
But I don't know how to continue expressing the terms as derivatives of some functions.

Answer & Explanation

George Blue

George Blue

Beginner2021-11-20Added 18 answers

Take the change of variable z=lny. So you would end up with the following relations
y=ez
y=zez
y=ezz+(z)2ez
Upon substitution (all ez's will cancel out), leaving you with a 2-nd order differential equation, which is easy to solve:
z=x
Stephanie Mann

Stephanie Mann

Beginner2021-11-21Added 25 answers

Consider yy instead of yy
yy(y)2=xy2
(yy)=x
Integrate
yy=x22+k
dyy=x22+kdx
lny=x36+k1x+k2
y(x)=k2ex36+k1x

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