An op-amp has 2 inputs, one having a resistance of 1000 W and the other having an input resistance of 5000 W.  The two inputs have a voltage of + 4 V and + 5 V respectively.  The feedback resistance is 2000 W.  What is the output voltage?    

(PP)

= - 2000( 0.004 + 0.001) (P)

Þ Vout = - 2000 × 0.005 = - 10 V (P)