document.write( "Question 1082829: The circle with equation x2 + y2 - 2x + 4y = 0 has centre C and radius r; where
\n" ); document.write( "1. C (1;-2) ; r = square root of 5
\n" ); document.write( "2.C (-1; 2) ; r = square root of 5
\n" ); document.write( "3. C (1;-4) ; r = square root of 17
\n" ); document.write( "4.C (-1; 4) ; r = 17
\n" ); document.write( "5. C (1;-2) ; r = 5\r
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Algebra.Com's Answer #696861 by Edwin McCravy(20059) $\"\"$ $\"About$

You can put this solution on YOUR website!

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document.write( "Instead of doing yours for you, I will do another\r\n" );
document.write( "one exactly like yours, which you can use as a model \r\n" );
document.write( "to do yours by:\r\n" );
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document.write( "Rearrange terms so that x terms are together and \r\n" );
document.write( "y terms are together.\r\n" );
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document.write( "We insert blanks where we must insert numbers\r\n" );
document.write( "which complete the squares:\r\n" );
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document.write( "We complete the square to find what goes in the first \r\n" );
document.write( "blanks on each side of the equation.\r\n" );
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document.write( "1. Multiply the coefficient of x by 1/2.\r\n" );
document.write( "    (-6)(1/2) = -3\r\n" );
document.write( "2. Square -3, get (-3)² = +9\r\n" );
document.write( "3. Add to both sides in the first blanks on each\r\n" );
document.write( "   side.\r\n" );
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document.write( "We also complete the square to find what goes in the \r\n" );
document.write( "remaining blanks on each side of the equation.\r\n" );
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document.write( "1. Multiply the coefficient of y by 1/2.\r\n" );
document.write( "    (+8)(1/2) = +4\r\n" );
document.write( "2. Square +4, get (+4)² = +16\r\n" );
document.write( "3. Add to both sides in the remaining blanks on each\r\n" );
document.write( "   side.\r\n" );
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document.write( "Next we factorise the first three terms on the left\r\n" );
document.write( "as (x-3)² and the last three terms on the left as (y+4)²\r\n" );
document.write( "and combine terms on the right as 26\r\n" );
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document.write( "We compare that to the standard equation for a circle:\r\n" );
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document.write( "and h=3, k=-4, and r=√26\r\n" );
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document.write( "So centre is (3,-4), radius = r = √26 \r\n" );
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document.write( "Now you can do yours exactly the same way.\r\n" );
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document.write( "Edwin

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