3-40Then, for a difference amplifier:With the same inputs that were used for the subtractor, (E1 = + 3 V; E2 = + 12 V) the output of thedifference amplifier should be five times the output of the subtractor (E_{out} = + 45 V).Following the same steps used for the subtractor:First compute the value of R2 plus R4:With this value, compute the current through R2 (I_{R2}):Next, compute the voltage drop across R2 (E_{R2}):Then, compute the voltage at point B:Since point A and point B will be at the same potential in an operational amplifier: