initial charges
Q1=C1ΔV
and Q2=C2ΔV
when the capacitors are connected they will acquire a common potential V
and charge will remain conserve so
qtotal=q1-q2 (since they are joined with opposite polarity)
so V=qtotal/Ceq.
V= q1-q2 / C1+C2
just put values
and finally Q'1=C1V
and Q'2=C2V