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Equation of a circle

  1. Oct 18, 2009 #1
    1. The problem statement, all variables and given/known data

    find the equation of a circle with centre of (2,-4) and y-intercept 1

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 18, 2009 #2
    The equation of a circle of radius r centered at the point (a,b) is given by (x-a)2+(y-b)2=r2. Since you already are given the point (a,b), all you need to find is the radius of the circle. Can you use the information that a y-intercept is (0,1) to find the radius?
  4. Oct 18, 2009 #3
    Thank you so much I didn't know it was that simple xD ok then can I ask something else:

    A circle with a centre (5,4) intersects the x-axis 3 units from the origin. Find the possible equations of the circle.

    Never mind i got it :D
    Last edited: Oct 18, 2009
  5. Oct 19, 2009 #4
    Ok, cool!
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