High input resistance and high gain Inverting amplifier can be needed in some applications.
In such case an even larger feedback resistor is required. Too large resistors have issues like precision, availability and excessive stray capacitance.
The here below circuit is a way to maintain both a high input resistance, a high gain and still using not too large feedback resistors.
Questions:

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1. Rin=100kohm
2. By using the usual ideal op-amp approximations, you note that the voltage at the T intersection of the three resistors is just Vin. So Vin= -Vout* 0.99/(0.99+100) and Av=Vout/Vin=-102.
(0.99 is the value of the parallel of the 1kohm and the 100kohm resistors).
1. Rin=100kohm
2. By using the usual ideal op-amp approximations, you note that the voltage at the T intersection of the three resistors is just Vin. So Vin= -Vout* 0.99/(0.99+100) and Av=Vout/Vin=-102.
(0.99 is the value of the parallel of the 1kohm and the 100kohm resistors).