The equation of the circle passing through the points of intersection of the circles
\[
x^2+y^2-2x-4y+1=0,
\]
\[
x^2+y^2-4x-2y+4=0
\]
and having its centre on the line
\[
x-2y-3=0
\]
is
Show Hint
If a circle passes through the common points of two circles \(S_1=0\) and \(S_2=0\), use
\[
S_1+\lambda(S_2-S_1)=0.
\]
Then apply the extra condition (centre, radius, tangent, etc.) to determine \(\lambda\).