1 1/3-7/12+9/20-11/30+13/42-15/56= (写出主要过程)

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1 1/3-7/12+9/20-11/30+13/42-15/56= (写出主要过程)
1 1/3-7/12+9/20-11/30+13/42-15/56= (写出主要过程)

1 1/3-7/12+9/20-11/30+13/42-15/56= (写出主要过程)
1又1/3-7/12+9/20-11/30+13/42-15/56
=1+1/3-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)
=1+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=1-1/8
=7/8

1/3-7/12+9/20-11/30+13/42-15/56=1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8=-1/8