Circles ‌S1:x2+y2−2y−3=0‌ and ‌ ‌S2:x2+y2−8x−18y+93=0 ‌C1≡(0,1)‌ and ‌r1=2 ‌C2≡(4,9)‌ and ‌r2=2 Since circles have same radius, centre of the smallest circle C3 is collinear with C1 and C2 and mid point of C1C2. ∴‌‌C3≡(2,5)