1/1×2+1/2×3+1/3×4+1/4×5+1/5×6+1/6×7+1/7×8=

如题所述

1/(1×2)=(1/1)-(1/2)
1/(2×3)=(1/2)-(1/3)
1/(3×4)=(1/3)-(1/4)
1/(4×5)=(1/4)-(1/5)
……
1/(7×8)=(1/7)-(1/8)
则这个式子的值=(1/1)-(1/8)=7/8
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第1个回答  2013-03-31
1/1×2+1/2×3+1/3×4+1/4×5+1/5×6+1/6×7+1/7×8
= (1/1)- (1/2) + (1/2)-(1/3)+(1/3)-(1/4)+ (1/4)-(1/5)+ (1/5)-(1/6)+(1/6)-(1/7)+(1/7)-(1/8)
= 1-1/8
= 7/8
第2个回答  2012-06-10
7/8
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