document.write( "Question 723780: Could you please teach me how to evaluate the sum of the following series?
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Algebra.Com's Answer #443392 by AnlytcPhil(1806)\"\" \"About 
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document.write( "1 + 2 – 3 + 4 – 5 + 6 – 7 + … + 2000\r\n" );
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document.write( "That has 2000 terms.  Let's write in the next to\r\n" );
document.write( "the last three terms:\r\n" );
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document.write( "1 + 2 – 3 + 4 – 5 + 6 – 7 + … + 1998 - 1999 + 2000\r\n" );
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document.write( "We put parentheses in like this:\r\n" );
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document.write( "1 + (2 – 3) + (4 – 5) + (6 – 7) + … + (1998 - 1999) + 2000 \r\n" );
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document.write( "Only the 1 on the left and the 2000 on the right are not in\r\n" );
document.write( "parentheses.  Those are the only two numbers that are not\r\n" );
document.write( "in parentheses so the other 1998 of the 2000 numbers are in\r\n" );
document.write( "parentheses.  Since there are two numbers in each set of \r\n" );
document.write( "parentheses there are one-half of 1998 or 999 sets of \r\n" );
document.write( "parentheses.\r\n" );
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document.write( "Every one of those 999 sets of parentheses has -1 in it.\r\n" );
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document.write( "So we have 999 negative one's which makes -999 plus the 1 on the left \r\n" );
document.write( "and the 2000 on the right.  That makes the sum -999+1+2000 = 1002\r\n" );
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document.write( "Edwin
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