Câu 13: (1,0 điểm) Tính: a) [TH_TL3] $\frac{1}{5}$ + |$\frac{-4}{5}$| b) [VD_TL6] $\frac{11}{7}$.($\frac{-1}{9}$) + $\frac{11}{7}$.($\frac{-2}{3}$)

`a . ` `1/5+|(-4)/5|`

`=` `1/5+4/5`

`=` `(1+4)/5`

`=` `5/5`

`=` `1`

$\\$

`b . ` `11/7*((-1)/9)+11/7*((-2)/3)`

`=` `11/7*((-1)/9+(-2)/3)`

`=` `11/7*(-7/9)`

`=` `-11/9`

`#me`