## Precalculus (6th Edition)

RECALL: The graph of the equation $x^2+y^2=r^2$ is a circle with center at $(0, 0)$ and a radius of $r$ units. The given equation can be written as $x^2+y^2=4^2$. Thus, the graph of this equation is a circle with center at $(0, 0)$ and a radius of $4$ units. To graph the circle, perform the following steps: (1) Plot the center $(0, 0)$. (2) Plot the four points 4 units directly above, below, to the left, and to the right of the center. (3) Connect the four points (excluding the center itself) using a curve to form a circle. (Refer to the graph in the answer part above.)