# Math Help - Do you know??

1. ## Do you know??

IF endpoints A(-7-1) and B(5,5)

How do you determine the equation of the circle passing through AB.

Need help with this, I can fiqure this out. Which equation do I use and what would the answer be.
Thanks for your help in advance.
Joanne

2. Hello bradycat!

You can first use the mid-point formula to find the center of the circle:

midpoint formula says:
$\frac{x_1+x_2)}{2} = h$ (x coordinate of center of circle)
and you do the same for your k (y coordinate) with the y coordinates of the given points.

So for your circle:

$\frac{-7+5}{2} = h$

$\frac{-1+5}{2} = k$

So the coordinate of the center of your circle are:
(h,k) or (-1,2)

Using that, see if you can figure out the standard form equation for the circle.

Good Luck!