Đáp án+Giải thích các bước giải:

`1.`

`a)` `(-1/2)^2+\sqrt{16/81}.{3}/4-|{-2}/3|`

`=` `1/4+4/9.{3}/4-2/3`

`=` `1/4+1/3-2/3`

`=` `7/12-2/3`

`=` `-1/12`

`b)` `(1/6+{-2}/3). 2021/2022+(5/6-1/3). 2021/2022`

`=` `-1/2.{2021}/2020+1/2.{2021}/2020`

`=` `2021/2020.(-1/2+1/2)`

`=` `2021/{2020}.0`

`=` `0`

`c)` $\dfrac{9^4.7^6}{7^8.3^7}$ 

`=`$\dfrac{(3^2)^4.7^6}{7^8.3^7}$ 

`=` $\dfrac{3^8.7^6}{7^8.3^7}$ 

`=` $\dfrac{3.1}{7^2.1}$ 

`=` `3/49`

`2.`

`a)` `5/6-x=2/3`

`x=5/6-2/3`

`x=5/6-4/6`

`x=1/6`

`b)` `{x+3}/-2=3/4`

`x+3=3/4.-2`

`x+3=-3/2`

`x=-3/2-3`

`x=-9/2`

`c)` `|x+2/5|+1/2=1\frac{1}{2}`

`|x+2/5|+1/2=3/2`

`|x+2/5|=3/2-1/2`

`|x+2/5|=1`

⇒ `x+2/5=1` hoặc `x+2/5=-1`

`x=1-2/5` hoặc `x=-1-2/5`

`x=3/5` hoặc `x=-7/5`