document.write( "Question 103514: Determine the center and radius of each circle and sketch graph: x^2-10x+y^2+8y=-10 \n" ); document.write( "
Algebra.Com's Answer #75323 by Fombitz(32388)\"\" \"About 
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\"x%5E2-10x%2By%5E2%2B8y=-10\"
\n" ); document.write( "The quickest way is to complete the square for both x and y. Then compare your equation to the equation of a circle and pick off the center of the circle and the radius.
\n" ); document.write( "\"%28x%5E2-10x%2BA%29=x%5E2%2B2B%2BB%5E2=%28x%2BB%29%5E2\" Completing the square for x.
\n" ); document.write( "\"%28y%5E2%2B8y%2BC%29=x%5E2%2B2D%2BD%5E2=%28x%2BD%29%5E2\"Completing the square for y.
\n" ); document.write( "where \"2B=-10\" and \"A=B%5E2\"
\n" ); document.write( "and \"2D=8\" and \"C=D%5E2\"
\n" ); document.write( "Let's solve for B and A.
\n" ); document.write( "\"2B=-10\"
\n" ); document.write( "\"highlight%28B=-5%29\"
\n" ); document.write( "\"A=B%5E2\"
\n" ); document.write( "\"highlight%28A=25%29\"
\n" ); document.write( "Let's solve for D and C.
\n" ); document.write( "\"2D=8\"
\n" ); document.write( "\"highlight%28D=4%29\"
\n" ); document.write( "\"C=D%5E2\"
\n" ); document.write( "\"highlight%28C=16%29\"
\n" ); document.write( "\"x%5E2-10x%2By%5E2%2B8y=-10\"
\n" ); document.write( "\"%28x%5E2-10x%2BA%29%2B%28y%5E2%2B8y%2BC%29=-10%2BA%2BC\"Add A and C to both sides.
\n" ); document.write( "\"%28x%2BB%29%5E2%2B%28y%2BD%29%5E2=-10%2BA%2BC\"Substitute with the completed squares from above.
\n" ); document.write( "\"%28x-5%29%5E2%2B%28y%2B4%29%5E2=-10%2B25%2B16\"Substitute your calculated values for A,B,C,D.
\n" ); document.write( "\"%28x-5%29%5E2%2B%28y%2B4%29%5E2=-10%2B25%2B16\"
\n" ); document.write( "\"%28x-5%29%5E2%2B%28y%2B4%29%5E2=31\"
\n" ); document.write( "\"%28x-h%29%5E2%2B%28y-k%29%5E2=R%5E2\" The equation of a circle centered at (h,k) with a radius R.
\n" ); document.write( "In this case,
\n" ); document.write( "(h,k)=(5,-4) and
\n" ); document.write( "\"R%5E2=31\"
\n" ); document.write( "\"R=sqrt%2831%29\"
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