1/30+1/42+1/56+1/72简便算法

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1/30+1/42+1/56+1/72简便算法1/30+1/42+1/56+1/72简便算法1/30+1/42+1/56+1/72简便算法1/30+1/42+1/56+1/72=(1/5-1/6)+(

1/30+1/42+1/56+1/72简便算法
1/30+1/42+1/56+1/72简便算法

1/30+1/42+1/56+1/72简便算法
1/30+1/42+1/56+1/72
=(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)
=1/5-1/9
=4/45

1/30+1/42+1/56+1/72
=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1/5-1/9
=4/45

1/30+1/42+1/56+1/72=(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)=1/5-1/9=9/45-5/45=4/45