The standard equation of a circle is expressed as
(x - h)^2 + (y - k)^2 = r^2
where
h is the x coordinate of the center of the circle
k is the y coordinate of the center of the circle
r is the radius of the circle
From the information given,
h = 2
k = 1
r = 3
Thus, the equation of the circle would be
(x - 2)^2 + (y - 1)^2 = 3^2
(x - 2)^2 + (y - 1)^2 = 9