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If 1 + 2-3 + 4-5 + 6-7 + 8-9 + , is the sum of the first 2000 numbers written down by taking two positive and two negative integers from 1 What is the sum of the first 2000 numbers? Why?
1+2-3+4-5+6-7+8-9+……
=1+(2-3)+(4-5)+(6-7)+(8-9)+…… (1998-1999) + 2000, [there are 2000 numbers from 1 to 2000, excluding 1 and 2000, there are 999 parentheses in 1998 / 2]
=2001-999
=1002
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