What is the center and radius of
K(5,5) L(6,-2) M(2,-4)
I try it but it's not equal to each other. Please help me
Huh. where's your work? What do you even mean? Here's one way. The center lies at the intersection of the perpendicular bisectors of two chords.
KL has slope -7 and midpoint (11/2,3/2)
KM has slope 3 and midpoint (7/2,1/2)
So now the center lies at the intersection of
y - 3/2 = 1/7 (x - 11/2)
y - 1/2 = -1/3 (x - 7/2)
The center is at C=(2,1)
The radius CK is 5
So the equation is (x-2)^2 + (y-1)^2 = 25
Or, you can brute-force it out by solving
(5-h)^2 + (5-k)^2 = r^2
(6-h)^2 + (-2-k)^2 = r^2
(r-h)^2 + (-4-k)^2 = r^2
which method did you try?