document.write( "Question 153709: Find the radius of a circle with the equation x2 + y2 - 6x - 12y + 36 = 0 \n" ); document.write( "

Algebra.Com's Answer #113266 by orca(409) $\"\"$ $\"About$

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Note that the equation of a circle in standard form is
\n" ); document.write( " $\"%28x-a%29%5E2%2B%28y-b%29%5E2=r%5E2\"$
\n" ); document.write( "where (a,b) is the center of the circle, r is the radius.
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\n" ); document.write( "First write the equation in standard form
\n" ); document.write( " $\"x2+%2B+y2+-+6x+-+12y+%2B+36+=+0\"$
\n" ); document.write( " $\"x%5E2-6x%2By%5E2-12y%2B36=0\"$
\n" ); document.write( " $\"x%5E2-6x%2B3%5E2-3%5E2%2By%5E2-12y%2B6%5E2-6%5E2%2B36=0\"$
\n" ); document.write( " $\"x%5E2-6x%2B3%5E2%2By%5E2-12y%2B6%5E2%2B36-3%5E2-6%5E2=0\"$
\n" ); document.write( " $\"%28x%5E2-6x%2B3%5E2%29%2B%28y%5E2-12y%2B6%5E2%29%2B36-9-36=0\"$
\n" ); document.write( " $\"%28x-3%29%5E2%2B%28y-6%29%5E2-9=0\"$
\n" ); document.write( " $\"%28x-3%29%5E2%2B%28y-6%29%5E2=3%5E2\"$
\n" ); document.write( "So the radius is 3.
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