document.write( "Question 974831: The sum of the following is 1 + 3 - 5 + 7 + 9 - 11+ 13......... 3n terms
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Algebra.Com's Answer #596766 by Edwin McCravy(20056) $\"\"$ $\"About$

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The sum of the following is 1 + 3 - 5 + 7 + 9 - 11+ 13......... 3n terms
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document.write( "The given sequence is the sum of two arithmetic sequences, 3n terms of\r\n" );
document.write( "the first sequence and n terms of the second sequence:\r\n" );
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document.write( "1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23 + ... + 3nth term\r\n" );
document.write( "      -10         - 22           - 34           - 46 - ... -  nth term\r\n" );
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document.write( "1 + 3 - 5 + 7 + 9 - 11 + 13 + 15 - 17 + 19 + 21 - 23 + ...     ?\r\n" );
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document.write( "The first sequence has 3n terms, but first we find the sum of n terms \r\n" );
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document.write( "and since it has 3n terms, we replace n by 3n and get the sum of 3n terms,\r\n" );
document.write( " or  \r\n" );
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document.write( "The second sequence -10-22-34-46- ... has only n terms:\r\n" );
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document.write( "Adding the two sums:  \r\n" );
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document.write( "Answer: \r\n" );
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document.write( "Edwin

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