AP EAMCET Engineering 22 Sep 2020 Shift 1 Paper

Equation of given circle
x2+y2−2x−4y−20=0
⇒‌‌(x−1)2+(y−2)2=25......(i)
Having centre C1(1,2) and radius 5 units.
∵ Another circle touches the circle (i) at point (5,5) having radius 5 units, so centre ' C2 ' of the second circle is collinear with C1 and point (5,5) is the mid-point of C1C2, so C2(9,8).
So, equation of the second circle is
(x−9)2+(y−8)2=25
⇒‌‌x2+y2−18x−16y+120=0