# Finding input resistance for this circuit

How do I find the input resistance for this circuit. I think it should be infinite but not able to analyse properly. Thanks.

If $(1+RG) \neq 0$, then the current is zero and so the input impedance in infinite. Otherwise the circuit doesn't have a unique solution.
To see this, note that $i = -GV_x$, where $i$ is the current entering the device. Since $V_x = R i$, this gives $i = -GRi$ or $(1+RG) i = 0$.