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document.write( "10, 30, 60, 100, 150, 210, ...\r\n" );
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document.write( "Find the sequence of differences to see if it is an arithmetic sequence\r\n" );
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document.write( "30-10, 60-30, 100-60, 150-100, 210-150, ...\r\n" );
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document.write( "Simplifying\r\n" );
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document.write( "20, 30, 40, 50, 60, ...\r\n" );
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document.write( "This is an arithmetic sequence, so the nth term is quadratic:\r\n" );
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document.write( "
\r\n" );
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document.write( "Substitute n=1,2,3, an = 10, 20 and 30\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" );
document.write( "
\r\n" );
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( "That gives us the system of equations to solve:\r\n" );
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document.write( "
\r\n" );
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document.write( "The solution is A=5, B=5, C=0\r\n" );
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document.write( "So the nth term\r\n" );
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document.write( "\r\n" );
document.write( "\r\n" );
document.write( "becomes\r\n" );
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document.write( "
\r\n" );
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document.write( "or\r\n" );
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document.write( "
\r\n" );
document.write( "\r\n" );
document.write( "Edwin
\n" );
document.write( "![\"\"](\"/images/stars/stars-13.gif\")
