Bài 5. (1,0 điểm) Tính A = $\frac{1}{2.5}$+ $\frac{1}{5.8}$+ $\frac{1}{8.11}$+...+ $\frac{1}{92.95}$+ $\frac{1}{95.98}$ 

$\color{green}{\triangleright \triangleright\texttt{LuKieBoy} \color{pink}{\texttt{SK} \triangleleft \triangleleft}}$

Đáp án+Giải thích các bước giải:

 `A=1/(2.5)+1/(5.8)+1/(8.11)+...+1/(92.95)+1/(95.98)`

`=>A=1/3 .(3/(2.5)+3/(5.8)+3/(8.11)+...+3/(92.95)+3/(95.98)`

`=>A=1/3 .(1/2-1/5+1/5-1/8+1/8-1/11+...+1/92-1/95+1/95-1/98)`

`=>A=1/3  . (1/2-1/98)`

`=>A=1/3 .(49/98-1/98)`

`=>A=1/3 . 24/49`

`=>A=24/147`

`=>A=8/49`

Vậy `A=8/49`