<PRE><B>Question 200661</B>
x^2 + y^2 + 2x - 6y - 6 =0
x^2 + y^2 + 2x - 6y = 6
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You have to complete the squares for the x and y terms.
x^2 + 2x + 1 is the x
y^2 - 6y + 9 is the y
1 and 9 have to be added to the left side, so add 10 to the right side.
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x^2 + 2x + 1  + y^2 - 6y + 9 = (x+1)^2 + (y-3)^2 = 6 + 10
The radius is sqrt(16)
r = 4

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