Question

What is the equation of a circle with center (6,4) that passes through the coordinate (2,1)?

Answer 1

The answer is going to be (2,2) 

Answer 2

first find the radius of circle by finding the length from center to the given point

well we  need the square of radius  r^2 = (6-2)^2 + (4-1)^2 = 25

equation of circle is (x - a)^2 + (y - b)^2 = r^2  where (a,b) is the center
so our circle is  
       (x - 6)^2 + ( y - 4)^2 = 25