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Homework Help: Radius of Circle

  1. May 6, 2009 #1
    1. What are the radius and center of this circle? x^2+4x+y^2-3y=0

    2. Relevant equations

    3. Another question on my final review I dont recall exactly how to set up or what steps I need to do in order to solve this problem. Any help is appreciated
  2. jcsd
  3. May 6, 2009 #2


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    Gold Member

    If I gave you the equation in the form [itex](x-a)^2+(y-b)^2=r^2[/itex], could you tell me the location of the center of the circle and its radius?

    If so, just complete the square for both x and y in your above equation in order to get it into this form.
  4. May 6, 2009 #3


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    The equation of a circle is of the form (x-a)^2+(y-b)^2=r^2. So you want to write x^2+4x as (x-a)^2+constant. In other words complete the square.
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