SOLUTION: Find the radius of a circle with the equation x2 + y2 - 6x - 12y + 36 = 0

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Question 153709: Find the radius of a circle with the equation x2 + y2 - 6x - 12y + 36 = 0
Answer by orca(409) About Me  (Show Source):
You can put this solution on YOUR website!
Note that the equation of a circle in standard form is
%28x-a%29%5E2%2B%28y-b%29%5E2=r%5E2
where (a,b) is the center of the circle, r is the radius.
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First write the equation in standard form
x2+%2B+y2+-+6x+-+12y+%2B+36+=+0
x%5E2-6x%2By%5E2-12y%2B36=0
x%5E2-6x%2B3%5E2-3%5E2%2By%5E2-12y%2B6%5E2-6%5E2%2B36=0
x%5E2-6x%2B3%5E2%2By%5E2-12y%2B6%5E2%2B36-3%5E2-6%5E2=0
%28x%5E2-6x%2B3%5E2%29%2B%28y%5E2-12y%2B6%5E2%29%2B36-9-36=0
%28x-3%29%5E2%2B%28y-6%29%5E2-9=0
%28x-3%29%5E2%2B%28y-6%29%5E2=3%5E2
So the radius is 3.