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May 16th, 2010, 11:28 AM   #1
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Finding the center and radius of a circle?

Hi,
So I have the following equation: x^2-12x+84=y^2+16y and I am trying to solve for the center and radius of the circle. I have been able to reduce it to (x-6)^2 - (y-^2 = 16 but the problem is that the standard form of equation is (x - h)^2 + (y - k)^2 = r^2 not (x - h)^2 - (y - k)^2 = r^2. Any ideas on how to change - to a +?
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May 16th, 2010, 12:06 PM   #2
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Re: Finding the center and radius of a circle?

Equation of a conic section:



If and the equation is a circle, but .

Reference: http://en.wikipedia.org/wiki/Conic_s...an_coordinates
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May 16th, 2010, 03:59 PM   #3
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The equation x - 12x + 84 = y + 16y reduces to (x - 6) - (y + 8) = -112. It's not a circle! Should y have been -y?
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May 16th, 2010, 04:00 PM   #4
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Re: Finding the center and radius of a circle?

Quote:
Originally Posted by thyrgle
Hi,
So I have the following equation: x^2-12x+84=y^2+16y and I am trying to solve for the center and radius of the circle. I have been able to reduce it to (x-6)^2 - (y-^2 = 16 but the problem is that the standard form of equation is (x - h)^2 + (y - k)^2 = r^2 not (x - h)^2 - (y - k)^2 = r^2. Any ideas on how to change - to a +?
You can't - you've got a hyperbola.
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May 16th, 2010, 04:10 PM   #5
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Re: Finding the center and radius of a circle?

Delete, please.
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