1/3+1/12+1/20+1/30+1/42+1/56=?

来源：学生作业帮编辑：神马作文网作业帮分类：数学作业时间：2024/11/12 06:52:46

1/3+1/12+1/20+1/30+1/42+1/56=?
写出简算过程

注确定第一项是1/3吗
1/3+1/12+1/20+1/30+1/42+1/56
=1/3+1/3x4+1/4x5+1/5x6+1/6x7+1/7x8
=1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8
=1/3+1/3-1/8 （中间的正负抵消了）
=16/24-3/24
=13/24
再问：是1/6
再答：
1/6+1/12+1/20+1/30+1/42+1/56
=1/2x3+1/3x4+1/4x5+1/5x6+1/6x7+1/7x8
=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 （中间的正负抵消了）
=3/8

1/2+1/6+1/12+1/20+1/30+1/42+1/56=? 1/12+1/20+1/30+1/42+1/56+1/72+1/90=? 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=? 1/2+1/6+1/12+1/20+1/30+1/42+1/56= 1/12+1/20+1/30+1/42+1/56+1/72= 等于多少? 1/6+1/12+1/20+1/30+1/42+1/56=? 1/20+1/30+1/42+1/56= 1+1/2+1/6+1/12+1/20+1/30+1/42+1/56+.1/132= 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+190+1/110=? 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90= 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=多少