1. The problem statement, all variables and given/known data Solve Laplace's equation on the rectangle 0< x< L, 0< y< H with the boundary conditions du/dx(0, y) = 0, du/dx(L, y)=y, du/dy(x, 0)=0, U(x, H)=x. 2. Relevant equations 3. The attempt at a solution I would be able to solve it by separation of variables if the last boundary condition were du/dx(x,H)=x. How can I apply the last boundary condition? Does principle of superposition work?