clc
//ex2.6
//we display the equations in scilab as follows
disp('At node 1:')
disp('(V1/R1)+((V1-V2)/R2)+i_s=0')      //KCL at node 1
disp('At node 2:')
disp('((V2-V1)/R2)+(V2/R3)+((V2-V3)/R4)=0')      //KCL at node 2
disp('At node 3:')
disp('(V3/R5)+((V3-V2)/R4))=i_s')      //KCL at node 3