数学题简算,1/2+1/6+1/12……+1/72+1/90

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数学题简算,1/2+1/6+1/12……+1/72+1/90

数学题简算,1/2+1/6+1/12……+1/72+1/90
数学题简算,1/2+1/6+1/12……+1/72+1/90

数学题简算,1/2+1/6+1/12……+1/72+1/90
=(1-1/2)+(1/2-1/3)+(1/3-1/4)……+(1/8-1/9)+(1/9-1/10)
=1-1/10
=9/10

1/2+1/6+1/12……+1/72+1/90 =1-1/2+1/2-1/3+1/3-1/4+.........+1/8-1/9+1/9+1/10
=1+1/10=11/10

1\2+1\2-1\3+1\3-1\4+1\4-1\5~```````1\8-1\9+1\9-1\10
=1-1\10
=9\10

这太简单了:1-1/2+1/2-1/3+1/3-1/4+1/4-1/5.........1/9-1/10=9/10(中间的都销掉了)