Answer:
(5 - 1)^2 + (1 - 1)^2 = 4^2
Explanation:
Circle equation: ( x - h )^2 + ( y - k )^2 = r^2
(h,K) is the coordinate of the center.
Center: (1,1)
(x,y) choose a point that could be the radius. (I choose the one on the top left side).
Point: (5,1)
Diameter: 8
Radius: 4
Plug in:
( x - h )^2 + ( y - k )^2 = r^2
(5 - 1)^2 + (1 - 1)^2 = 4^2 (or 16)
Solve to see if it's true,
(5 - 1)^2 + (1 - 1)^2 = 4^2 (or 16)
4^2 + 0^2 = 4^2
16 = 16 (This is true, therefore, the equation is correct).