document.write( "Question 1099554: What is the general term of the sequence -1, 3, -6, 10, -15, 21 ....? \n" ); document.write( "
Algebra.Com's Answer #714012 by Edwin McCravy(20056)\"\" \"About 
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document.write( "{an}: -1, 3, -6, 10, -15, 21 ....?\r\n" );
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document.write( "Double them and get\r\n" );
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document.write( "{2an}: -2, 6, -12, 20, -30, 42 ....\r\n" );
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document.write( "Write them as the product of two integers:\r\n" );
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document.write( "{2an}: -1ﾗ2, 2ﾗ3, -3ﾗ4, 4ﾗ5, -5ﾗ6, 6ﾗ7 ....\r\n" );
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document.write( "To get the alternating signs we use the factor (-1)nﾗ\r\n" );
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document.write( "{2an}: (-1)1ﾗ1ﾗ2, (-1)2ﾗ2ﾗ3, (-1)3ﾗ3ﾗ4, (-1)4ﾗ4ﾗ5, (-1)5ﾗ5ﾗ6, (-1)6ﾗ6ﾗ7 ....\r\n" );
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document.write( "So the general term for 2an is  \r\n" );
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document.write( "2an (-1)nﾗnﾗ(n+1)\r\n" );
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document.write( "So the general term for an is half that, so\r\n" );
document.write( "we divide both sides by 2:\r\n" );
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document.write( "     (-1)nﾗnﾗ(n+1)\r\n" );
document.write( "an = 覧覧覧覧覧覧予r\n" );
document.write( "           2\r\n" );
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document.write( "or eliminating the multiplication symbols:\r\n" );
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document.write( "     (-1)nn(n+1)\r\n" );
document.write( "an = 覧覧覧覧覧予r\n" );
document.write( "          2\r\n" );
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document.write( "Edwin
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