document.write( "Question 841929: Determine the sum of the first 40 terms of the following series:
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Algebra.Com's Answer #507523 by Edwin McCravy(20056)\"\" \"About 
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document.write( "                             2+2+5+4+8+8+11+16+...\r\n" );
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document.write( "The odd-numbered terms are   2 + 5 + 8 + 11  + ... \r\n" );
document.write( "The even-numbered terms are    2 + 4 + 8  + 16 +...\r\n" );
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document.write( "The first 40 terms are 20 terms of each of those sequences\r\n" );
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document.write( "The first sequence is:\r\n" );
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document.write( "2 + 5 + 8 + 11  + ... \r\n" );
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document.write( "which is an arithmetic sequence with a1=2, d=3, n=20\r\n" );
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document.write( "so we use this sum formula \r\n" );
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document.write( "Sn = \"n%2F2\"[2a1 + (n-1)d] \r\n" );
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document.write( "S20 = \"20%2F2\"[2(2) + (20-1)3] = 10[4 + (19)3] = 10[4+57] = 10[61] = 610\r\n" );
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document.write( "The second sequence\r\n" );
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document.write( "2 + 4 + 8  + 16 +...\r\n" );
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document.write( "which is an geometric sequence with a1=2, r=2, n=20\r\n" );
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document.write( "so we use this sum formula \r\n" );
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document.write( "Sn = \"a%5B1%5D%28r%5En-1%29%2F%28r-1%29\"\r\n" );
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document.write( "S20 = \"2%282%5E20-1%29%2F%282-1%29\" = \"2%281048576-1%29%2F1\" = \"2%281048575%29\" = \"2097150\"\r\n" );
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document.write( "Adding the two sums together\r\n" );
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document.write( "610 + 2097150 = 2097760  \r\n" );
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document.write( "Edwin
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