arlf44
幼苗
共回答了21个问题采纳率:90.5% 举报
|1-1/2| + |1/2-1/3| + |1/3-1/4| + |1/2009-1/2010|
=1-1/2 + 1/2-1/3 + 1/3-1/4 + 1/2009-1/2010
=1-1/4 + 1/2009-1/2010
=3/4+1/(2009*2010)
=(3*2009*1005+2)/(2*2009*2010)
如果:
|1-1/2| + |1/2-1/3| + |1/3-1/4| +……+ |1/2009-1/2010|
=1-1/2 + 1/2-1/3 + 1/3-1/4 + ……+1/2009-1/2010
=1- 1/2010
=2009/2010
1年前
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