简便计算 1-1/6+1/42+1/56+1/72+1/90 = = = =简便计算 1-1/6+1/42+1/56+1/72+1/90 === =

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简便计算 1-1/6+1/42+1/56+1/72+1/90 = = = =
简便计算 1-1/6+1/42+1/56+1/72+1/90
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1-1/6+1/42+1/56+1/72+1/90
=1-1/6+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)+(1/9-1/10)
=1-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10
=1-1/10
=9/10

1-1/6+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)+(1/9-1/10)
=1-1/10
=9/10