I am trying to solve a linear fourth order differential equation (for example for y[x]) with boundary values (not an initial value problem), but where the coefficients are functions of x and not constants. The system seems to want to do some sort of transformation but cannot and then gives me error messages;the resulting solution is not accurate and does even satisfy the boundary conditions I put in. I suspect that the new boundary value solver in Mathematica 3.0 can only really deal with linear second order equations.
Does anyone have any expertise, experience, or suggestions for dealing with the 4th order system. Making a new variable g[x]=h''[x] and then solving two equations for g[x] and h[x] does not work; for boundary values the system apparently wants only ONE equation.
Any help? Is there any documentation or user notebooks on this?