Bài 1: (2,0 điểm) Thực hiện phép tính: a) $\frac{-8}{19}$.$\frac{16}{31}$ + $\frac{-8}{19}$.$\frac{15}{31}$ - $\frac{11}{19}$ b) $\sqrt{(-5)²}$.(-$\frac{1}{5}$)² : [($\frac{-1}{3}$)² + $\sqrt{\frac{1}{4}}$ - $\sqrt{\frac{16}{9}}$] c) $\sqrt{121}$ - $\sqrt{225}$ + $\sqrt{\frac{25}{4}}$ d) |$\frac{-11}{3}$| + ($\frac{-1}{2}$)² - |4$\frac{1}{2}$ + (-3,25)|

`K`

`a, -8/19 . 16/31 + -8/19 . 15/31 -11/19`

=-8/19 . 1 -11/19`

`=-19/19`

`=-1`

`b, \sqrt((-5)^2) . (-1/5)^2 : [(-1/3)^2 + \sqrt(1/4) - \sqrt(16/9)]`

`=5 . 1/25 : [1/9 + 1/2 - 4/3]`

`=1/5 : (-13/18)`

`=-18/65`

`c, \sqrt(121)-\sqrt(225) + \sqrt(25/4)`

`=11-15 + 5/2`

`=-4+5/2`

`=-3/2`

`d, |-11/3| + (-1/2)^2 - |4 1/2 + (-3,25)|`

`=11/3 + 1/4 - |4,5 -3,25|`

`=11/3 + 1/4 - 1,25`

`=8/3`