Solve Op Amp Circuit Problem: Find V2/V1 w/Potentiometer

[farahtc]

Homework Statement

The op amp circuit shown bellow is intended to provide any gain between -10 (for k=0) and +10 (for k=1) by adjusting the potentiometer. Let R1 and R2 have the scaled values, show that..

V2/V1= {r1/(r1+10k)} [-11/{1+(10kr1/r1+10k)}] + [r2/r2+10(1-k)] [1+ {11/1+10kr1/r1+10k}]

Homework Equations

The Attempt at a Solution

i have no idea how to write nodal equations for a potentiometer. If anyone tell me how to do that, i can figure out the rest by myself. thanks

 

[unplebeian]

Think of the potentiometer as 2 resistors in series with values 10k and 10(1-k). That's all.