# Weak maximum principle of Discrete type

I am reading Partial differential equations written by Jurgen Just (Third edition) chapter 4, and I want to do some exercises. I think that I need some hints to solve the problem 4.2:

Let $x_0 \in \Omega_h$ have neighbours $x_1,\ldots ,x_{2d}$.We consider a difference operator Lu for u:$\bar\Omega_h\rightarrow\Bbb R$,