Bài 1: (2 điểm) Tính hợp lý (nếu có thể) a) $\frac{-1}{3}$- $(\frac{2}{3}$ + $\frac{1}{5})$  b) $\frac{-3}{7}$ + $\frac{3}{5}$+ $\frac{-4}{7}$+ $\frac{-5}{4}$+ $\frac{2}{5}$  c) $1\frac{1}{4}$- $4\frac{1}{4}$ .$\frac{9}{34}$  d) $\frac{-1}{5}$. $\frac{-3}{2}$+ $\frac{4}{-15}$. $\frac{3}{2}$ - $2\frac{1}{3}$ . $\frac{3}{2}$ 

Bài `1:`

`a)` `(-1)/3 - (2/3+1/5)`

`=(-1)/3 - 2/3 - 1/5`

`=(-1)-1/5`

`=-6/5`

`b)` `(-3)/7 + 3/5 + (-4)/7 + (-5)/4 + 2/5`

`=((-3)/7 + (-4)/7) + (3/5+2/5)+(-5)/4`

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

`=0+(-5)/4`

`=(-5)/4`

`c)` `1 1/4 - 4 1/4 . 9/34`

`=5/4 - 17/4 . 9/34`

`=(-12)/4 . 9/34`

`=(-3) . 9/34`

`=(-27)/34`

`d)` `(-1)/5 . (-3)/2 + 4/(-15) . 3/2 - 2 1/3 . 3/2`

`=1/5 . 3/2 + (-4)/15 . 3/2 - 7/3 . 3/2`

`=3/2.(1/5+(-4)/15 - 7/3)`

`=3/2.(3/15 - 4/15 - 35/15)`

`=3/2.(-36/15)`

`=(-18)/5`