1/2+1/6+1/20+1/30+1/42+1/56+1/72等于多少?
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1/2+1/6+1/20+1/30+1/42+1/56+1/72等于多少?
1/2+1/6+1/20+1/30+1/42+1/56+1/72等于多少?
1/2+1/6+1/20+1/30+1/42+1/56+1/72等于多少?
原式
=1/(1*2)+1/(2*3)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)+1/(8*9)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1+(-1/2+1/2)+(-1/3+1/3)+(-1/4+1/4)+(-1/5+1/5)+(-1/6+1/6)+(-1/7+1/7)+(-1/8+1/8)-1/9
=1+0+0+0+0+0+0+0-1/9 (这步可略)
=1-1/9
=8/9
29/36
原式=(1-1/2)+(1/2-1/3)+(1/3-1/4)+…+(1/8-1/9)
=1-1/9
=8/9
题目中应该是写掉了一个“+1/12”
原式
=1/(1*2)+1/(2*3)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)+1/(8*9)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1+(-1/2+1/2)+(-1/3+1/3)+(-1/4+1/4)+(-1/5+1/5)+(-1/6+1/6)+(-1/7+1/7)+(-1/8+1/8)-1/9
=1-1/9
=8/9
2%1+6%1+12%1+20%1+30%1
1/2+1/6+1/12+1/20+1/30
1/2,-1/6,1/12,-1/20,1/30
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
1+1/2+1/12+1/6+1/20+1/30+1/40+1/56
1/2+1/6+1/12+1/20+1/30+1/42+1/56 简算
1/2+1/6+1/12+1/20+1/30+1/42+1/56简算,
简便运算: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的简便计算
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怎么算
1/2+1/6+1/12+1/20+1/30+.1/380+1/420=
1+1/2+1/6+1/12+1/20+1/30+1/42=?
1/2+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等于多少
2/1+6/1+12/1+20/1+30/1+42/1+56/1=
1/2+1/6+1/12+1/20+1/30+...+1/9702+1/9900