I'm having some problems in finding the general solution of a linear second-order hyperbolic PDE in canonical form $$ u_{xy} = F(u_x, u_y, u, x, y) $$ where $F$ is some function.
Specifically I'm interested in solving this PDE in canonical form $$ u_{xy} + k(u_x + u_y) + (k^2-\sigma^2P(x-y))u = f(x)f(y) $$ where $k$, $\sigma$ are constant parameters and $P(x)$, $f(x)$ are some known function.
More than knowing the general solution of the second equation I'm mainly interested in knowing what is the general strategy for solving the first, generic, linear second-order hyperbolic PDE.
Most material I have read suggests only to find the canonical form of the equation (which I was able to do) but does not give further instructions on how to solve this canonical equation, but I have the impression there must be some cookbook recipe for doing so.
Thank you very much!