AP EAMCET Engineering 20 Apr 2019 Shift 2 Paper

Consider the given circles.
S1:x2+y2+4y−7=0
S2:2x2+2y2+3x+5y−9=0
And
S3:x2+y2+y=0
The radical axis of circle S1 and S2 is x−y−1=0
The radical axis of circle S2 and S3 is x+y−3=0
Thus, the coordinate of radical centre is (2,1) and the radius is,
r‌‌=√4+1+8−7
‌‌=√6
Hence, the equation of the required circle is,
(x−2)2+(y−1)2=6
x2+y2−4x−2y−1=0