(1)求1,-2,3,-4,...,2009,-2010这2010个数的和!(2)1 1 1 1------- +-------+-------+...+--------------1*2 2*3 3*4 2010*2011

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(1)求1,-2,3,-4,...,2009,-2010这2010个数的和!(2)1111-------+-------+-------+...+--------------1*22*33*42010

(1)求1,-2,3,-4,...,2009,-2010这2010个数的和!(2)1 1 1 1------- +-------+-------+...+--------------1*2 2*3 3*4 2010*2011
(1)求1,-2,3,-4,...,2009,-2010这2010个数的和!
(2)1 1 1 1
------- +-------+-------+...+--------------
1*2 2*3 3*4 2010*2011

(1)求1,-2,3,-4,...,2009,-2010这2010个数的和!(2)1 1 1 1------- +-------+-------+...+--------------1*2 2*3 3*4 2010*2011
(1)和=1-2+3-4+5-6+……+2009-2010
=(1-2)+(3-4)+(5-6)+……+(2009-2010)
=(-1)×(2010÷2)
=-1005
(2)原式=1-1/2+1/2-1/3+1/3-1/4+……+1/2010-1/2011
=1-1/2011
=2010/2011
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