Solution: 1. the output attempts to do whatever is necessary to make the voltage difference between the inputs zero. 2. The inputs draw no current Comments on 1: The voltage gain of a real op-amp is so high that a fraction of a millivolt input will swing the output over its full range. Practically, that amounts to rule1 Comments on 2: The input current is so low (0.08 microamps for the 741, picoamps for an FET-input op-amp) that rule 2 is practically correct.