Standard form of the equation of a circle

kingofamericans

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Aug 18, 2012
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Hey everyone. I'm doing college math and in this problem I am especially stuck on the part of the problem where I am supposed to somehow get some of these numbers into fraction form and the program I'm using (MyMathLab) is not really explaining how to do it at all. Here is the problem:

A circle has the equation x2+y2-x+6y+9=0. Graph the circle using the center (h, K) and radius r. Find the intercepts, if any, of the graph.

I don't care so much about anyone graphing the circle anywhere near as much as just figuring out how to get the center and radius. Thanks a lot in advance.
 
Sure would like to know what you've tried.

x2+y2-x+6y+9=0

It's called "Completing the Square"

Hint:

x^2 - x + WHAT + y^2 +6y + WhatElse + 9 - WHAT - WhatElse = 0

More Hints:

(1/2)^2 = 1/4

(6/2)^2 = 9

Seriously, don't make me do the whole thing!
 
Thanks!

I figured it out with the help of both you and the Kahn Academy guy haha. Sorry for not initially giving enough information.
 
Notice how you also gave no helpful information at the end. :(
 
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