# How do you write an equation for a circle with center (2,-1) and radius 3?

Feb 20, 2016

The required equation is
(x-2)^2 + (y+1))^2=9

#### Explanation:

The distance formula is

$\sqrt{{\left(x - h\right)}^{2} + {\left(y - k\right)}^{2}} = r$

Now,equation of a circle is

$\left({\left(x - h\right)}^{2} + {\left(y - k\right)}^{2}\right) = {r}^{2}$

Thus,an equation for a circle with center (2,-1) and radius 3 is

${\left(x - 2\right)}^{2} + {\left(y - \left(- 1\right)\right)}^{2} = {3}^{2}$

(x-2)^2 + (y+1))^2=9