Hi... I was here trying to solve an OpAmp problem, but I'm stuck. I can't find a way of writing an equation for v_R1 in function of va and vb, which I know and confirmed to be equal to v1 (measured with the voltmeter). I found v_R1 = (R1*vo)/(R1 + R2) and that vo = ((R1 + R2)*v_R1)/R1 By the OpAmp thumbs-up rules, I know that the OpAmp will try everything it cans to keep v+ and v- at the same potential, so v1 = v_R1. Now, I need to get rid of v1 from the vo equation, but I can't find the way! Any help would be appreciated!