A4 = [-1      1      0    0      0;...
       1  -2002      1    0      0;...
       0      1     -1    0      0;...
       0   1000      0    1      0;...
       0   1000      0    0      1];
 
detA4 = det(A4)
 
A3 = [-1      1      0      0      0;...
      1  -2002      1   1000   1000;...
      0      1     -1      0      0;...
      0   1000      0  -1000      0;...
      0   1000      0      0  -1000]
 
detA3 = det(A3)
 
A2 = [-2 1 0 1;...
1 -2 1 0;...
0 1 -2 1;...
1 0 1 -2]
 
detA2 = det(A2)
 
A = zeros(7, 7);
A(1+0,1+0)= -1;
A(1+1,1+0)= 1;
A(1+0,1+1)= 1;
A(1+1,1+1)= -2002;
A(1+2,1+1)= 1;
A(1+3,1+1)= 1000;
A(1+4,1+1)= 1000;
A(1+1,1+2)= 1;
A(1+2,1+2)= -1;
A(1+3,1+3)= -1000;
A(1+1,1+3)= 1000;
A(1+5,1+3)= -1;
A(1+4,1+4)= -1000;
A(1+1,1+4)= 1000;
A(1+6,1+4)= -1;
A(1+3,1+5)= 1;
A(1+4,1+6)= 1;
 
x1 = [0,0,0,0,0,1,0]';
x2 = [0,0,0,0,0,0,1]';
 
A^(-1);
 
A^(-1) * x1
A^(-1) * x2;
 
disp(A);

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