document.write( "Question 636105: Write the equation of a circle that passes through (7,-1) and has its center at (-2,4). \n" ); document.write( "
Algebra.Com's Answer #400734 by jim_thompson5910(35256)\"\" \"About 
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\"%28x-h%29%5E2%2B%28y-k%29%5E2=r%5E2\" Start with the general equation of a circle.\r
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\n" ); document.write( "\n" ); document.write( "\"%28x--2%29%5E2%2B%28y-4%29%5E2=r%5E2\" Plug in \"h=-2\" and \"k=4\" (since the center is the point (h,k) ).\r
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\n" ); document.write( "\n" ); document.write( "\"%287--2%29%5E2%2B%28-1-4%29%5E2=r%5E2\" Plug in \"x=7\" and \"y=-1\" (this is the point that lies on the circle, which is in the form (x,y) ).\r
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\n" ); document.write( "\n" ); document.write( "\"%289%29%5E2%2B%28-5%29%5E2=r%5E2\" Combine like terms.\r
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\n" ); document.write( "\n" ); document.write( "\"81%2B25=r%5E2\" Square each term.\r
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\n" ); document.write( "\n" ); document.write( "\"106=r%5E2\" Add.\r
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\n" ); document.write( "\n" ); document.write( "So because \"h=-2\", \"k=4\", and \"r%5E2=106\", this means that the equation of the circle with center (-2,4) that goes through the point (7,-1) is \r
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\n" ); document.write( "\n" ); document.write( "\"%28x%2B2%29%5E2%2B%28y-4%29%5E2=106\".
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