Bài 1. (2 điểm) Tính hợp lý nếu có thể: a) $\frac{-2}{3}$ - $\frac{1}{2}$ + $\frac{5}{6}$  b) $\frac{3}{5}$ + $\frac{-14}{15}$ . $\frac{-3}{7}$  c) ($\frac{-3}{11}$ -$\frac{5}{7}$) - ($\frac{8}{11}$- 2 + $\frac{9}{7}$)  d) $\frac{7}{12}$. $3\frac{1}{4}$- $\frac{7}{12}$. $\frac{1}{4}$+ $\frac{7}{12}$ 

Đáp án`+`Giải thích các bước giải :

`a)``(-2)/3-1/2+5/6`

`=-4/6-3/6+5/6`

`=-1/3`

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`b)``3/5+(-14)/15 . (-3)/7`

`=3/5+2/5`

`=5/5`

`=1`

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`c)``((-3)/11-5/7)-(8/11-2+9/7)`

`=-3/11-5/7-8/11+2-9/7`

`=(-3/11-8/11)-(5/7+9/7)+2`

`=-11/11-14/7+2`

`=-1-2+2`

`=-1`

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`d)``7/12 .3 1/4-7/12 . 1/4+7/12`

`=7/12 .(13/4-1/4+1)`

`=7/12 .4`

`=7/3`