AMU Engineering 2017 solved paper Solved Paper

Let equation of circle be
(x−h)2+(y−k)2=52, where 5 is the radius of the circle.
Also, the radius of given circle
c1:x2+y2−2x−4y−20=0 is given by
√1+4+20=5 units ∵ Two circles touch each other externally.
∴(5,5) is the mid-point of line segment joining (h,k) and (1,2)
⇒5=

h+1

2

,5=

k+2

2

⇒h=9,k=8
∴ Equation of circle becomes(x−9)2+(y−8)2=52