document.write( "Question 126884: Could you please help me solve this? find the center (h,k) and radius r of the circle. I have no idea how to work out.
\n" ); document.write( "x^2+y^2-12x+6y+35=0
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Algebra.Com's Answer #92943 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
Start with the general formula for a circle
\n" ); document.write( "\"%28x+-+h%29%5E2+%2B+%28y+-+k%29%5E2+=+r%5E2\"
\n" ); document.write( "Somehow you have to get your equation into that form
\n" ); document.write( "\"x%5E2+%2B+y%5E2+-+12x+%2B+6y+%2B+35+=+0\"
\n" ); document.write( "Group the x terms together and the y terms together
\n" ); document.write( "and subtract \"35\" from both sides
\n" ); document.write( "\"x%5E2+-+12x+%2B+y%5E2+%2B+6y+=+-35\"
\n" ); document.write( "Now do the operation called completing the square
\n" ); document.write( "on the x terms and the y terms
\n" ); document.write( "You do that by taking 1/2 of the coefficient of
\n" ); document.write( "x (or y), squaring it, then add it to both sides
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\n" ); document.write( "Notice that this is the exact same equation
\n" ); document.write( "I started with because I added the same thing to BOTH sides
\n" ); document.write( "\"x%5E2+-+12x+%2B+36+%2B+y%5E2+%2B+6y+%2B+9+=+-35+%2B+36+%2B+9\"
\n" ); document.write( "Now you can get this into the form
\n" ); document.write( "\"%28x+-+h%29%5E2+%2B+%28y+-+k%29%5E2+=+r%5E2\"
\n" ); document.write( "\"%28x+-+6%29%5E2+%2B+%28y+%2B+3%29%5E2+=+10\"
\n" ); document.write( "If you just match up the terms, you see that
\n" ); document.write( "\"h+=+6\"
\n" ); document.write( "\"k+=+-3\"
\n" ); document.write( "\"r%5E2+=+10\"
\n" ); document.write( "\"r+=+sqrt%2810%29\"
\n" ); document.write( "So, the center is at (6,-3) and the radius is \"sqrt%2810%29\"
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