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document.write( "The red line is the given line 2x-3y = -7,\r\n" );
document.write( "The green and blue lines are radii of the circle.\r\n" );
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document.write( "We need the slope of the given red line so we can get \r\n" );
document.write( "the equation of the green line, which is perpendicular\r\n" );
document.write( "to it:\r\n" );
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document.write( " 2x-3y = 7\r\n" );
document.write( " -3y = -2x+7\r\n" );
document.write( " 
\r\n" );
document.write( " 
<--equation of red line\r\n" );
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document.write( "Comparing to y = mx+b, slope of red line = 
\r\n" );
document.write( "The green line is perpendicular to the red line, so\r\n" );
document.write( "the green line's slope is the negative reciprocal of\r\n" );
document.write( " which is 
.\r\n" );
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document.write( "The green line passes through (1,3), so we use the point-\r\n" );
document.write( "slope formula to find its equation\r\n" );
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document.write( "
\r\n" );
document.write( "
\r\n" );
document.write( "clear fraction by multiplyng through by 2\r\n" );
document.write( "
\r\n" );
document.write( "
\r\n" );
document.write( "
<-- eq. of the green line \r\n" );
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document.write( "The center of the circle (h,k) is a point on\r\n" );
document.write( "the green line, so we substitute (x,y) = (h,k)\r\n" );
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document.write( "eq. 1: 
\r\n" );
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document.write( "We use the distance formula to find an expression\r\n" );
document.write( "for the length of the green and blue lines, which\r\n" );
document.write( "will be the radius, so\r\n" );
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document.write( "
\r\n" );
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document.write( "Square both sides:\r\n" );
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document.write( "
\r\n" );
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document.write( "
\r\n" );
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document.write( "
\r\n" );
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document.write( "Simplify by cancelling h2's and k2's \r\n" );
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document.write( "
\r\n" );
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document.write( "
\r\n" );
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document.write( "Divide through by 4\r\n" );
document.write( "
\r\n" );
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document.write( "So we put this with equation (1) above\r\n" );
document.write( "as a system of equations:\r\n" );
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document.write( "
\r\n" );
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document.write( "Solve that system by substitution and get\r\n" );
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document.write( "(h,k) = (5,-3) <-- center of circle\r\n" );
document.write( "\r\n" );
document.write( "We find the radius from\r\n" );
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document.write( "
\r\n" );
document.write( " \r\n" );
document.write( "
\r\n" );
document.write( "\r\n" );
document.write( "
\r\n" );
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document.write( "
\r\n" );
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document.write( "So the radius is \r\n" );
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document.write( "Equation of circle:\r\n" );
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document.write( "
\r\n" );
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document.write( "
\r\n" );
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document.write( "
\r\n" );
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document.write( "Edwin
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document.write( "![\"\"](\"/images/stars/stars-13.gif\")
