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% Example 4-4: Resistor Network
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% Define variables
V1=20; V2=12; V3=40;
R1=18; R2=10; R3=16; R4=6;
R5=15; R6=8; R7=12; R8=14;
% Matrix A
A = [-(R1+R2+R3) R2 R3 0
    R2 -(R2+R4+R5+R7) R4 R7
    R3 R4 -(R3+R4+R6) R6
    0 R7 R6 -(R6+R7+R8)]
% Vector B
B = [-V1; 0; V2; -V3]
% Solve for currents
I = A\B