(Solved): This is a solution for solving CMRR for Op-Amp. Can anyone explain how they got the circled equatio ...

This is a solution for solving CMRR for Op-Amp. Can anyone explain how they got the circled equation above ?

CMRR \( =\frac{|A|}{\left|A_{c m}\right|} \quad \) CMRR \( =20 \log _{10} \frac{|A|}{\left|A_{c m}\right|} \) \( v_{o}=A v_{i d}+A_{c m} v_{i c m} \) \( v_{i d}=v_{1}-v_{2} \quad v_{i c m}=\left(v_{1}+v_{2}\right) / 2 \) \( v_{1}=v_{i c m}+\frac{v_{d}}{2} \quad v_{2}=v_{i c m}-\frac{v_{d}}{2} \)