Answer:
A. x^2 + y^2 = 36
Step-by-step explanation:
The equation of a circle is usually written in the form
(x-h)^2 + (y-k)^2 = r^2
Where (h,k) is the center and r is the radius
The center is at the origin so (h,k) = (0,0) and the radius is 6 so r=6
x^2 + y^2 = 6^2
or x^2 +y^2 = 36
