# How do you write the equation for a circle with center at (-1, -3) and a radius of 6?

May 10, 2016

${\left(x + 1\right)}^{2} + {\left(y + 3\right)}^{2} = 36$
The general equation for a circle is ${\left(x - h\right)}^{2} + {\left(y - k\right)}^{2} = {r}^{2}$ where the centre if the circle is $\left(h , k\right)$ and the radius is $r$.
Substituting in the values provided gives us ${\left(x - \left(- 1\right)\right)}^{2} + {\left(y - \left(- 3\right)\right)}^{2} = {6}^{2}$
${\left(x + 1\right)}^{2} + {\left(y + 3\right)}^{2} = 36$