Find the center and radius of the circle with the given equation.
-$$x ^ { 2 } + y ^ { 2 } = 9$$
A) $( 3,3 ) ; r = 9$
B) $( 0,0 ) ; r = 9$
C) $( 3,3 ) ; r = 3$
D) $( 0,0 ) ; r = 3$

Question

Quizplus · Accepted Answer

The equation of a circle in the standard form is $(x - h)^2 + (y - k)^2 = r^2$, where $(h, k)$ is the center of the circle and $r$ is the radius. The given equation $x^2 + y^2 = 9$ matches this form with $h = 0$, $k = 0$, and $r^2 = 9$, which means the center is $(0,0)$ and the radius is $\sqrt{9} = 3$.

Find the Center and Radius of the Circle with the Given