The equation for a circle with the given information would be (x - 4)^2 + (y + 1)^2 = 81.
This is because the base form of a circle is:
(x - x1)^2 + (y - y1)^2 = r^2
In which, x1 is the x coordinate of the center and y1 is the y coordinate of the center. r is the radius of the circle. So we plug in to those and simplify.
(x - 4)^2 + (y - -1)^2 = 9^2
(x - 4)^2 + (y + 1)^2 = 81
