September 7th, 2015, 03:16 PM  #1 
Newbie Joined: Mar 2015 From: Chicago Posts: 22 Thanks: 1  How to find the center?
Find the center and radius of the circle with equation x2 + y2 − 8x + 18y + 16 = 0. 
September 7th, 2015, 03:23 PM  #2 
Senior Member Joined: Jun 2015 From: England Posts: 731 Thanks: 204 
So what is the equation of a circle with centre (X1, Y1) and radius R? You have to manipulate the given expression to arrive at that form. You can do this by completing the squares for (X, X1) and (Y,Y1) or by Multiplying out the equation for the above circle and equating coefficients. 
September 7th, 2015, 10:40 PM  #3  
Senior Member Joined: Sep 2015 From: 4th Dimension Posts: 146 Thanks: 13 Math Focus: Everything (a little bit)  Quote:
 

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