let the distance between center and point (5,5) = d₁
let the distance between center and point (1,5) = d₂
let the distance between center and point (1,1) = d₃
The condition of the circle is d₁ = d₂ = d₃
Making two equations to find x , y
d₁² = d₂²
∴ (x-5)² + (y-5)² = (x-1)² + (y-5)²
∴ (x-5)² = (x-1)²
∴ x-5 = \pm (x-1) ⇒⇒⇒ positive sign unacceptable
∴ x-5 = -(x-1)
∴
x = 3
d₁² = d₃²
∴ (x-5)² + (y-5)² = (x-1)² + (y-1)²
substituting with x and simplifying the equation
∴
y = 3
∴center = (3,3)
The correct choice will be (C)
Answer ⇒⇒⇒ C. (3, 3)