How do you find the center and radius of the circle (x - 3) ^2 + (y + 1) ^2 = 9?

Feb 5, 2016

Center $\left(3 , - 1\right)$
$r a \mathrm{di} u s = 3$

Explanation:

The centre-radius form of a circle is ${\left(x - h\right)}^{2} + {\left(y - k\right)}^{2} = {r}^{2}$ with the centre being $\left(h , k\right)$ and $r$ as the radius.

Given this, we would know that the center of the circle is $\left(3 , - 1\right)$ and the radius is 3.

Luckily we are given the centre-radius form so we can easily get/compute for what was asked. However, if we are given the standard form of a circle, we should first do completing the square to transform it into its center-radius form.