# Second order ODE with non-constant coefficients

• Oct 21st 2011, 01:17 PM
toobusy
Second order ODE with non-constant coefficients
I am trying to solve y''+(3-1/x^2)y=0. Is it possible to solve by separation? Or will this require a series solution?
• Oct 21st 2011, 02:28 PM
HallsofIvy
Re: Second order ODE with non-constant coefficients
If by "separation" you mean writing it as $\frac{d^2y}{dx^2}= (\frac{1}{x^2}- 3)y$ and then to
$\frac{d^2y}{y}= (\frac{1}{x^2}- 3)dx^2$, then, no, you cannot "separate" a second order derivative like you can a first order derivative. The "differentials" dy and dx are defined in Calculus, but such things as " $d^2y$" and " $dx^2$" are NOT defined.
• Oct 21st 2011, 06:52 PM
Ackbeet
Re: Second order ODE with non-constant coefficients
Quote:

Originally Posted by toobusy
I am trying to solve y''+(3-1/x^2)y=0. Is it possible to solve by separation? Or will this require a series solution?

It's a homogeneous linear equation, and thus always has the zero solution. However, if you desire non-trivial solutions, then series is the way to go.
• Oct 21st 2011, 08:39 PM
toobusy
Re: Second order ODE with non-constant coefficients
Thanks! I just figured it out!