奥数:1/2+1/6+1/12+1/20+1/30+1/42+1/56 =
来源：学生作业帮助网 编辑：六六作业网 时间：2024/11/23 19:16:13
奥数:1/2+1/6+1/12+1/20+1/30+1/42+1/56 =
奥数:1/2+1/6+1/12+1/20+1/30+1/42+1/56 =
奥数:1/2+1/6+1/12+1/20+1/30+1/42+1/56 =
原式=1/1×2+1/2×3+……+1/6*7+1/7*8
=1-1/2+1/2-1/3……+1/6-1/7+1/7-1/8
=7/8
1/2+1/6+1/12+1/20+1/30+1/42+1/56
=1/2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8
=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
=1-1/8
=7/8
1/2+1/6＋1/12＋1/20＋1/30＋1/42＋1/56
=1/2+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)
=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)
=1-1/8
=7/8
原式＝1/2+1/（2*3）+1/（3*4）+1/（4*5）+1/（5*6）+1/（6*7）+1/（7*8）
＝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
＝1/2+1/2-1/8
＝1-1/8
＝7/8
1)1/2+1/6+1/12+1/20+1/30+1/42+1/56
=1/2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8
=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
=1-1/8
=7/8
2)计算器是干啥用的
原式=1/(1x2)+1/(2x3)+1/(3x4)+.....+1/(7x8)
=1-1/2+1/2-1/3+1/3-1/4+.....+1/7-1/8
=1-1/8
=7/8
1/2+1/6+1/12+1/20+1/30+1/42+1/56
=2/3+1/12+1/20+1/30+1/42+1/56
=9/12+1/20+1/30+1/42+1/56
=3/4+1/20+1/30+1/42+1/56
=3/80+1/30+1/42+1/56
=17/240+1/42+1/56
=123/280+1/56
=128/280
=16/35