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+//CHAPTER 1- D.C. CIRCUIT ANALYSIS AND NETWORK THEOREMS 
+//Example 21
+
+disp("CHAPTER 1");
+disp("EXAMPLE 21");
+
+//VARIABLE INITIALIZATION
+I=20;                             //current source in Amperes
+v1=10;                            //voltage source in Volts
+v2=40;                            //voltage source in Volts
+r1=8;                             //in Ohms
+r2=5;                             //in Ohms
+r3=4;                             //in Ohms
+r4=12;                            //in Ohms
+
+//SOLUTION
+
+req=r1+r2;                        //series combination of resistors
+rth=(req*r3)/(req+r3);            //parallel connection of resistors (Thevenin resistance)
+
+//by using nodal analysis, the following equations are obtained
+//(13)v1+(-8)v2=750.......eq (1)
+//(-4)v1+(9)v2=200........eq (2)
+//solving the equations by matrix mehod
+
+A=[13 -8;-4 9];
+b=[750;200];
+x=inv(A)*b;
+v1=x(1,:);                        //to access the 1st element of 2X1 matrix
+v2=x(2,:);                        //to access the 2nd element of 2X1 matrix
+vth=v2;                           //Thevenin voltage
+I=vth/(rth+r4);                   //Thevenin current
+disp(sprintf("By Thevenin Theorem, the value of I is %.3f A",I));
+
+//END