Bài 1. (2,5 điểm) Thực hiện phép tính (tính hợp lý nếu có thể): a) $\frac{5}{6}$ + $\frac{-11}{30}$ + $\frac{7}{5}$ b) ($\frac{-4}{5}$)².$\frac{57}{2}$ + $\frac{-7}{2}$.($\frac{-4}{5}$)² c) ($\frac{7}{25}$ - 1$\frac{2}{9}$) - ($\frac{23}{54}$ - $\frac{28}{25}$) + $\frac{-31}{54}$

Bài `1:`

`a) 5/6 + (-11)/30 + 7/5`

`= 25/30 - 11/30 + 42/30`

`= (25-11+42)/30`

`= 56/30=28/15`

`b) ((-4)/5)^2 * 57/2 + (-7)/2 * ((-4)/5)^2`

`= ((-4)/5)^2 * (57/2-7/2)`

`= 16/25 * 25`

`= 16`

`c) (7/25 -1 2/9)-(23/54-18/25)+(-31)/54`

`= 7/25 - 11/9 - 23/54 + 18/25 - 31/54`

`= (7/25+18/25)+(-23/54-31/54)-11/9`

`= 1-1-11/9`

`= -11/9`

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