KEAM 2014 Math Paper

Let S=x2+y2=16
At point (0,0)
S≡0+0−16=−16<0
At point (0,1)
S=0+1−16=−15<0Thus, both points lie inside the circle.
It means required circle touch inside the given circle.
So, the centre and radius of given circle are C(0,0) and r=4
since, the required circle is passing through centre (0,0)
∴ Diameter of required circle =4
and radius of required circle =‌

4

2

=2