# How do you write an equation for a circle given center (8,-9) and passes through (21,22)?

##### 1 Answer

Please see the explanation for steps leading to the equation.

#### Explanation:

The standard form for the equation of a circle is:

where

We are given that the center point is

NOTE: One can write

To find the value of r, substitute the given point, 21 for x and 22 for y, into equation [2]:

Substitute

Equation [3] is the standard form for the circle.