\( V_{out} = A \cdot V_{input} \)

where \( A \) is the Gain

\( A = 1 + \frac{R_2}{R_1} \)

\( V_{out} = A \cdot V_{input} \)

where \( A \) is the Gain

\( A = -\frac{R_2}{R_1} \)

For an inverting op-amp, the negative sign means the output voltage inverted compared to the input. Positive input results in a negative output, and negative input results in a positive output.