1/20+1/30+1/42+1/56简便计算,

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1/20+1/30+1/42+1/56简便计算,1/20+1/30+1/42+1/56简便计算,1/20+1/30+1/42+1/56简便计算,解原式=(1/4-1/5)+(1/5-1/6)+(1/6

1/20+1/30+1/42+1/56简便计算,
1/20+1/30+1/42+1/56
简便计算,

1/20+1/30+1/42+1/56简便计算,
解
原式
=(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)
=1/4+(1/5-1/5)+(1/6-1/6)+(1/7-1/7)-1/8
=1/4-18
=1/8

3/4+1/20+1/30+1/42+1/56+1/72
=(1-1/4)+(1/4-1/5)+(1/5-1/6)+(6/1-1/7)+(1/7-1/8)+(1/8-1/9)
=1-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1-1/9
=8/9
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简算题1/2+1/6+1/12+1/20+1/30+1/42+1/56 1/12+1/20+1/30+1/42+1/56+1/72 怎么简算? 怎样简算“1/2+1/6+1/12+1/20+1/30+1/42+1/56” 1/20+1/30+1/42+1/56简便计算, 1/3+1/12+1/20+1/30+1/42+1/56=?写出简算过程 1/20+1/30+1/42+1/56=1/20+1/30+1/42+1/56= 12分之1+20分之1+30分之1+42分之1+56分之1,这道题怎么简算? 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72 1/6加1/12加1/20加1/30加1/42加1/56加1/72加1/90怎样简算? 1/2+1/6+1/12+1/20+1/30+1/42+1/56 简算 1/2+1/6+1/12+1/20+1/30+1/42+1/56简算, 1/12+1/20+1/30+1/42+1/56+1/72+1/90 简便运算：1/2+1/6+1/12+1/20+1/30+1/42+1/56 2/1+6/1+12/1+20/1+30/1+42/1+56/1=? 1/12+1/20+1/30+1/42+1/56+1/72+1/90 1/6+1/12+1/20+1/30+1/42+1/56+1/72 简便计算 1/2 - 1/6 - 1/12 - 1/20 - 1/30 - 1/42 - 1/56怎么算