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Math Help - Finding Center And Radius of Circle

  1. #1
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    Finding Center And Radius of Circle

    x^2 + y^2 + 6x=0. How would I go about finding the radius and center? What's the basic method?

    -Thanks!
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    Moo
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    Hello,

    Quote Originally Posted by Hibijibi View Post
    x^2 + y^2 + 6x=0. How would I go about finding the radius and center? What's the basic method?

    -Thanks!
    To complete the squares

    I'll do it in a newly way to me... lol

    x^2+6x=x(x+6)=((x+3)-3)((x+3)+3)=(x+3)^2-3^2=(x+3)^2-9
    (I know you can do it in a shorter way... find it ! )

    Hence the equation becomes :

    (x+3)^2+y^2-9=0 \Longleftrightarrow (x+3)^2+y^2=9


    We know that the equation of a circle, center O(x_O,y_O) and radius R is :

    (x-x_O)^2+(y-y_O)^2=R^2


    Conclude
    Last edited by Moo; May 12th 2008 at 02:24 PM. Reason: replaced 0 by O
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