In the attached photo is the problem I have been trying to solve, having just started looking at Op amps. From the start they seem to be tricky. This one is wired in negative feedback and I am trying to find Vout. From my course notes I vaguely remember having to do voltage divider somewhere. Where would those points be?
Due to negative feedback, whatever it is (in an ideal op-amp), the node A in your picture will be pulled to match v+, so node A will be at virtual ground. That means no resistive divider is necessary, that's only if you have two or more resistors in the same current path. Here the virtual ground essentially forces the two input branches to be separate, because the voltage at v- is actively maintained by the power in the op-amp, no matter how the two input voltages, or even the resistance values change.
The current of the two separated input branches still adds, however, because it cannot go into the non-inverting op-amp input. Can you use this info to arrive at the solution now?
If you're still stuck, you can use the superposition theorem, it usually helps to simplify scenarios like these a lot (if the active device is ideal and linear, which we can assume it is).
