Final answer:
The input resistance for the inverting amplifier can be calculated using the formula Rin = Rf + Rin-noninv + (1 + A)Rin-noninv.
Step-by-step explanation:
The input resistance for the inverting amplifier, with an op-amp gain of A, is given by the formula:
Rin = Rf + Rin-noninv + (1 + A)Rin-noninv
Where Rf is the feedback resistor and Rin-noninv is the non-inverting input resistance.