Question

数学题〜急〜

1乘2乘3分之一+2乘3乘4分之1+.......+98乘99乘100分之1

（只有4分了，但还是真诚恳求大家帮助！请打出过程或做简单解释！谢谢！

Answer 1

Answer 2

1/(n-1)n(n+1)
=1/n*[1/ (n-1)(n+1)]
=1/2n*[2/ (n-1)(n+1)]
=1/2n*[1/(n-1)-1/(n+1)]
=1/2* [1/(n-1)n-1/n(n+1)]
接着你可以累加了

Answer 3

=1/2-1/3+1/3-1/4+1/4-1/5+……+1/99-1/100
=1/2-1/100
=49/100

追问

亲〜您貌似弄错题目了

追答

是的，我看成了二连乘了

Answer 4

原式=(2/1)×[(1×2)/1-(2×3)/1]+(2/1)×[(2×3)/1-(3×4)/1]+……+(2/1)×[(8×9)/1-(9×10)/1]
=(2/1)×[(1×2)/1-(9×10)/1]
=(2/1)×(2/1-90/1)
=45/11

Answer 5

1/1*2+1/2*3+1/3*4+……+1/99*100
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/99-1/100)
=1-1/2+1/2-1/3+1/3-1/4+……+1/99-1/100
=1-1/100
=99/100

就这样当中所有项都互相抵消，求采纳