document.write( "Question 261409: what is the equation fot the circle with a center of (-4,-7) and tangent to x=2? \n" ); document.write( "
Algebra.Com's Answer #192634 by Edwin McCravy(20060)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "To get the equation of a circle we need the center (h,k)\r\n" );
document.write( "and the radius r, and the standard equation for a circle\r\n" );
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document.write( "\"%28x-h%29%5E2%2B%28y-k%29%5E2=r%5E2\"\r\n" );
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document.write( "We have the center point, so all we need is the radius.\r\n" );
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document.write( "Let's plot the center (-4,-7) and draw the line \"x=2\" which is\r\n" );
document.write( "a vertical line through 2 on the x-axis, shown in green below:\r\n" );
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document.write( "We draw a horizontal line from the center over to where the\r\n" );
document.write( "circle is to be tangent to the green line, for that will be a\r\n" );
document.write( "radius for the circle, which we can also draw in::\r\n" );
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document.write( "Using the x-axis as a measuring stick, we can see that that radius\r\n" );
document.write( "is 6 units long, 4 units over to the y-axis and 2 units more on the\r\n" );
document.write( "right side of the y-axis, which makes the radius 6 units long.  So\r\n" );
document.write( "all that's left to do is substitute (h,k)= (-4,-7), and r=6 into the \r\n" );
document.write( "standard equation for a circle:\r\n" );
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document.write( "\"%28x-%28-4%29%29%5E2%2B%28y-%28-7%29%29%5E2=%286%29%5E2\"\r\n" );
document.write( "\"%28x%2B4%29%5E2%2B%28y%2B7%29%5E2=36\"\r\n" );
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document.write( "That's it.\r\n" );
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document.write( "Edwin
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