What is the diameter of the following circle: (x + 4)2 + (y – 9)2 = 18
recall that the general equation of a circle is given by
(x - h)^2 + (y - k)^2 = r^2
where the point (h,k) is the center of the circle, and r is the radius. thus in the given equation,
(x + 4)^2 + (y – 9)^2 = 18
18 = r^2
therefore,
r = sqrt(18) = 3*sqrt(2)
and so the diameter is
d = 2*r = 6*sqrt(2)
hope this helps~ :)