Answer:
x^2 + y^2 = 3^2
Step-by-step explanation:
Start with (x - h)^2 + (y - k)^2 = r^2.
If the center is at (0, 0), we then have x^2 + y^2 = r^2.
If this circle passes through (0, 9), then 0^2 + 9^2 = r^2, and r must be 3.
Then the standard equation of this circle i
x^2 + y^2 = 3^2
