Answer:
The answer is

Explanation:
In order to determine the equation of a circle, we have to know the formula about it.
The "standard form equation of a circle" is:

Where:
(h,k)= coordinates of the center of the circle. "h" is the "x" coordinate and "k" is the "y" coordinate.
r=radius of the circle.
So, we just need the center and radius to get the equation of a circle.
In this case:

I have attached an image that shows a graph of a circle.