What is the equation of the circle shown in the graph

The general equation for a circle is:
[tex](x-h)^2 + (y-k)^2 = r^2[/tex]

where (h,k) is center of circle
r = radius

For this example, from the graph you see the center is at (0,-3) and radius is 2.
h  = 0, k = -3, r = 2

Sub into general equation:
[tex](x-0)^2 + (y-(-3))^2 = 2^2 \\ \\ x^2 +(y+3)^2 = 4[/tex]