英超妹妹2
春芽
共回答了9个问题采纳率:66.7% 举报
-1乘1/2=-1+1/2,
-1/2乘1/3=-1/2+1/3,
-1/3乘1/4=-1/3+1/4
.
(1)
-1/n乘1/(n+1)=-1/n+1/(n+1)
(2)
(-1)X1/2+(-1/2)X1/3+(-1/3)X1/4+……+(-1/2011X1/2012)+(-1/2012*1/2013)
=-1+1/2-1/2+1/3-1/3+1/4-1/4+.-1/2011+1/2012-1/2012+1/2013.(前后2项相加为0)
=-1+1/2013
=-2012/2013
1年前
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