Answer:
x^2+y^2=9^2
Step-by-step explanation:
The standard equation of a circle is:
Where the center of a circle is (h,k) and r is the radius of the circle. In this case because a circle is equidistant from the center and we have a point where it passes through 9 that means that the radius is 9. However, since the standard equation states that we must write r in the form of this means that
. Therefore by plugging in the values we have: