Question 425281
The center is the midpoint of the endpoints, so the center is at (4, -4) (obtain this by taking the average of the x-coordinates, average of the y-coordinates). The radius of the circle is the distance from (4, -4) to, say, (12, 11). By the distance formula, this is equal to


{{{r = sqrt((12-4)^2 + (11-(-4))^2) = sqrt(8^2 + 15^2) = 17}}}


So the radius is 17.