If the center is at (0, 0) and if (0, -9) lies on the circle, then the radius must be 9.
In this case, the equation of this circle is
x^2 + y^2 = r^2 = 9^2.
Does (8, 717) satisfy this equation? No. 717^2 would be far outside of the circle. the distance from the center to the point (8, 17) is not the same as the radius
