Answer:
x^2 + y^2 = 9
Step-by-step explanation:
The standard equation of a circle with center at (h, k) and radius r is
(x - h)^2 + (y - k)^2 = r^2. Here h = 0, k = 0, x = 3 and y = 0:
(3 - 0)^2 + (0 - 0)^2 = r^2, or
9 = r^2. Thus, the radius is 3.
The equation of this circle is (x - 0)^2 + (y - 0)^2 = 9, or
x^2 + y^2 = 9
