When solving the above equation using ﬁnite diﬀerence method on square, in order to make it easy to see the internal structure of the A matrix using the standard 5 points Laplacian scheme, the following is a small function which generates the symbolic format of these equations for a given , the number of grid points on one edge. At the end of this note, the system equations are generated for . One can see the form of the matrix with the dominant diagonal.