= Solution
In the linear <inverting amplifier>, the non-inverting terminal is grounded and <negative feedback> connects the output to the inverting terminal. For large open-loop gain $A$, $V_o=A(V_+-V_-)$; a finite unsaturated output therefore requires $V_-\simeq V_+=0$. Thus
$$
\boxed{V_-\simeq0\quad\text{under stable negative feedback}.}
$$
This is a <virtual ground>: it has approximately ground potential, but it is not a conducting connection to ground. The ideal <operational amplifier> draws no input current, so input current flows through the feedback resistor. Saturation, loss of feedback, or insufficient bandwidth invalidates the approximation.
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