Bài 1: (2,0 điểm) Thực hiện phép tính: a) 3,5.$\frac{2}{21}$ - $\frac{5}{9}$ : $\frac{25}{3}$ + $\frac{1}{15}$ b) 16.($\frac{3}{20}$ - $\frac{2}{5}$)² + $\frac{3}{5}$ c) $\frac{-11}{3}$ : (1,5.$\sqrt{\frac{16}{9}}$ - $\frac{10}{3}$) d) ($\sqrt{\frac{81}{16}}$ + $\frac{-3}{4}$) : (-$\frac{3}{4}$)² - |$\frac{-27}{4}$ : 3²|

a) `3,5 . 2/21 - 5/9 : 25/3 + 1/15`

`= 7/2 . 2/21 - 5/9 . 3/25 + 1/15`

`= 1/3 - 1/15 + 1/15`

`= 1/3 + (1/15 - 1/15)`

`= 1/3 + 0`

`= 1/3`

b) `16 . (3/20 - 2/5)^2 + 3/5`

`= 16 . (3/20 - 8/20)^2 + 3/5`

`= 16 . (-5/20)^2 + 3/5`

`= 16 . (1/4)^2 + 3/5`

`= 16 . 1/16 + 3/5`

`= 1 + 3/5`

`= 5/5 + 3/5`

`= 8/5`

c) `(-11)/3 : (1,5 . sqrt{16/9} - 10/3)`

`= (-11)/3 : (3/2 . 4/3 - 10/3)`

`= (-11)/3 : (2 - 10/3)`

`= (-11)/3 : (6/3 - 10/3)`

`= (-11)/3 : (-4)/3`

`= (-11)/3 . 3/(-4)`

`= (-11)/(-4)`

`= 11/4`

d) `(sqrt{81/16} + (-3)/4) : (-3/4)^2 - | (-27)/4 : 3^2|`

`= (9/4 + (-3)/4) : 9/16 - | (-27)/4 : 9 |`

`= 6/4 : 9/16 - |(-27)/4 . 1/9|`

`= 3/2 . 16/9 - |(-3)/4|`

`= 8/3 - 3/4`

`= 32/12 - 9/12`

`= 23/12`