Hello everyone

I am new in mapple software and i am facing some proplem to tackle  Laplace equation and Poisson equation. I want to find out the potential psi given in two equations 

I want to solve following equ with finite difference method in order to find potential psi .In the second equation  n = concentration of electrons  ,p= concentration of holes and C= additional concentration ,q is electronic charge .

Can anyone suggeset how I can solve this type of partial differential equation with numerical method (FDM) in mapple?