Graph x^2+y^2=81

This is the form of a circle. Use this form to determine the center and radius of the circle.

Match the values in this circle to those of the standard form. The variable ${\displaystyle r}$ represents the radius of the circle, ${\displaystyle h}$ represents the x-offset from the origin, and ${\displaystyle k}$ represents the y-offset from origin.

The center of the circle is found at ${\displaystyle (h,k)}$.

These values represent the important values for graphing and analyzing a circle.