作业帮10/(1*2)+20/(1*2*3)+30/(1*2*3*4)+40/(1*2*3*4*5)+...+90/(1*2*
来源：学生作业帮 编辑：作业帮 分类：数学作业 时间：2024/05/16 17:56:31
10/(1*2)+20/(1*2*3)+30/(1*2*3*4)+40/(1*2*3*4*5)+...+90/(1*2*3*4*5*6*4*8*9*10)=?
原式+10/(1*2*3*4*5*6*4*8*9*10)
=10/(1*2)+……+80/1*2*3*4*5*6*4*8*9)+90/(1*2*3*4*5*6*4*8*9*10)+10/(1*2*3*4 *5*6*4*8*9*10)
=10/(1*2)+……+80/1*2*3*4*5*6*4*8*9)+ 100/(1*2*3*4*5*6*4*8*9*10)
=10/(1*2)+……+80/1*2*3*4*5*6*4*8*9)+ 10/(1*2*3*4*5*6*4*8*9)
=…………
=10/(1*2)+10/(1*2)
=10
所以原式=10-10/(1*2*3*4*5*6*4*8*9*10)
=多少自己算
=10/(1*2)+……+80/1*2*3*4*5*6*4*8*9)+90/(1*2*3*4*5*6*4*8*9*10)+10/(1*2*3*4 *5*6*4*8*9*10)
=10/(1*2)+……+80/1*2*3*4*5*6*4*8*9)+ 100/(1*2*3*4*5*6*4*8*9*10)
=10/(1*2)+……+80/1*2*3*4*5*6*4*8*9)+ 10/(1*2*3*4*5*6*4*8*9)
=…………
=10/(1*2)+10/(1*2)
=10
所以原式=10-10/(1*2*3*4*5*6*4*8*9*10)
=多少自己算
10/(1*2)+20/(1*2*3)+30/(1*2*3*4)+40/(1*2*3*4*5)+...+90/(1*2*
10/(1*2)+20/(1*2*3)+30/(1*2*3*4)+40/(1*2*3*4*5)++...+90/(1*2
1*2*3+2*4*6+...10*20*30/2*3*4+...+20*30*40
1+2+3+4+10+20+30+40+1234=?
4.{1,5,10}{2,10,20}{3,15,30}{4,20,40}{ }.
1/1×2+1/2×3+1/3×4+1/4×5+...+1/39×40
1/2+1/3+2/3+1/4+2/4+3/4+1/5+2/5+3/5+4/5.+1/40+2/40+.+38/40+3
1＝10 2＝20 3＝30 4＝40 5＝50
1+2+3+4+5+6+7+8+9+10+20+30+40+50.+100
1/1*2*3+1/2*3*4+1/3*4*5+.+1/18*19*20
1/1*2*3 + 1/2*3*4 + 1/3*4*5 +.+1/20*21*22
(1/2+1/3+1/4+…1/39+1/40)+(2/3+2/4+2/5+…2/39+2/40)+(3/4+3/5+3