làm chi tiết ra mọi người ơi

`a) -47 . 69 + 31 . (-47) - (-155) + 5 . (-3)²``

`= -47 . 69 + 31 . (-47) + 5 . 31 + 5 . 9`

`= -47 . (69 + 31) + 5 . (31 + 9)`

`= -47 . 100 + 5 . 40`

`= -47 . 100 + 100 . 2`

`= 100 . (-47 + 2)`

`= 100 . (-45)`

`= -4500`

`b)` $\dfrac{27}{23}$ `-` $\dfrac{-5}{21}$ `-` $\dfrac{4}{23}$ `+` $\dfrac{16}{21}$ `+` $\dfrac{1}{2}$

`= `($\dfrac{27}{23}$ `-` $\dfrac{4}{23}$`) + (`$\dfrac{5}{21}$ `+` $\dfrac{16}{21}$`) +` $\dfrac{1}{2}$

`= 1 + 1 +` $\dfrac{1}{2}$

`=` $\dfrac{5}{2}$

`c)` $\dfrac{-8}{9}$ `+` $\dfrac{1}{9}$ `.` $\dfrac{2}{9}$ `+` $\dfrac{1}{9}$ `.` $\dfrac{7}{9}$

`=` $\dfrac{-8}{9}$ `+` $\dfrac{1}{9}$ `. (`$\dfrac{2}{9}$ `+` $\dfrac{7}{9}$`)`

`=` $\dfrac{-8}{9}$ `+` $\dfrac{1}{9}$ `. 1`

`=` $\dfrac{-7}{9}$ . 

`c) `$\dfrac{3}{4}$ `+ (`$\dfrac{5}{9}$ `+` $\dfrac{-3}{4}$`)`

`=` $\dfrac{3}{4}$ `+` $\dfrac{5}{9}$ `+` $\dfrac{-3}{4}$

`=` $\dfrac{3}{4}$ `+` $\dfrac{-3}{4}$ `+` $\dfrac{5}{9}$

`= 0 +` $\dfrac{5}{9}$

`=` $\dfrac{5}{9}$

`d) (`$\dfrac{2}{3}$ `+` $\dfrac{1}{6}$`) +` $\dfrac{-5}{6}$

`=` $\dfrac{4}{6}$ `+` $\dfrac{1}{6}$ `+` $\dfrac{-5}{6}$

`=` $\dfrac{0}{6}$ `= 0`

`e)` $\dfrac{-5}{7}$ `.` $\dfrac{2}{11}$ `+` $\dfrac{-5}{7}$ `.` $\dfrac{9}{11}$ `+` 1$\dfrac{5}{7}$

`= `$\dfrac{-5}{7}$ `. (`$\dfrac{2}{11}$ `+` $\dfrac{9}{11}$`) + 1`$\dfrac{5}{7}$

`=` $\dfrac{-5}{7}$ `. 1 + 1`$\dfrac{5}{7}$

`= 1`

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