I = -1/100x99 - 1/99x98 - 1/98x97 - ... -1/2x1

Ta có :

`I = (-1)/(100.99) - 1/(99.98) - 1/(98.97) - ... - 1/(2.1)`

`=> I=-(1/(100.99) + 1/(99.98) + 1/(98.97)+...+1/(2.1))`

`=> I = -(1/(1.2) + 1/(2.3) + 1/(3.4) + ... + 1/(99.100))`

`=> I = -(1/1 - 1/2 + 1/2 -1/3 + 1/3 - 1/4 + ... + 1/99 - 1/100)`

`=> I = -(1/1 - 1/100)`

`=> I = -99/100`

Vậy `I = (-99)/100`

`#dtkc`