Answer
center is at (0, 0)
radius = 3 units
See attached image for the graph.
Work Step by Step
RECALL:
The standard equation of a circle whose center is at (0, 0) and radius $r$ is:
$x^2+y^2=r^2$
The given equation is similar to the standard form given above.
Thus, the given equation represents a circle with center at (0, 0) and
$r^2=9
\\r=\sqrt9
\\r=3$
Therefore, the given circle has:
center at (0, 0)
radius = 3 units
Plot the points (-3, 0), (3, 0), (0, -3), and (0, 3) then connect them using a curve to form a circle.
Or, use a graphing calculator to have the graph attached in the answer part above.