function X=jacobi_G(A,n)
%A為非奇異矩陣

D=zeros(n);
L=zeros(n);
U=zeros(n);
for i=1:n
    for j=1:n
        if i==j
            D(i,j)=A(i,j);          
        end
    end
end
for i=2:n
   for j=1:n-1
    if j<i
        L(i,j)=A(i,j);
    end
   end
end
for i=1:n-1
   for j=2:n
    if j>i
        U(i,j)=A(i,j);
    end
   end
end
G=-inv(D)*(L+U);
D,L,U