简算题1/2+1/6+1/12+1/20+1/30+1/42+1/56

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简算题1/2+1/6+1/12+1/20+1/30+1/42+1/56简算题1/2+1/6+1/12+1/20+1/30+1/42+1/56简算题1/2+1/6+1/12+1/20+1/30+1/42

简算题1/2+1/6+1/12+1/20+1/30+1/42+1/56
简算题1/2+1/6+1/12+1/20+1/30+1/42+1/56

简算题1/2+1/6+1/12+1/20+1/30+1/42+1/56
1/2+1/6+1/12+1/20+1/30+1/42+1/56
=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)
=1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8
=1/2-1/8
=4/8-1/8
=3/8