Let right surface of plate A has charge =x And total charge on plate A=q1 ∴q1= Charge on left surface of plate A+ Charge on right surface of plate A =‌
q1+q2
2
+x ⇒x=q1−‌
q1+q2
2
=‌
2q1−q1−q2
2
=‌
q1−q2
2
Let potential difference between two plates =v For capacitor we know, q=CV ∴‌