Đáp án:
Bài `2:`
`a)-1/4-3/4:x=-11/36`
`<=>3/4-x=-1/4-(-11/36)`
`<=>3/4-x=1/18`
`<=>x=3/4-1/18`
`<=>x=25/36`
`b)5/7+2/3.x=3/10`
`<=>2/3.x=3/10-5/7`
`<=>2/3.x=-29/70`
`<=>x=-87/140`
`c)|-2/7-x|+1=4`
`<=>|-2/7-x|=4-1`
`<=>|-2/7-x|=3`
$\Leftrightarrow\left[\begin{matrix} x-\dfrac{2}{7}=3\\ x-\dfrac{2}{7}=-3\end{matrix}\right.\Leftrightarrow\left[\begin{matrix} x=3+\dfrac{2}{7}\\ x=-3+\dfrac{2}{7}\end{matrix}\right.\Leftrightarrow\left[\begin{matrix} x=-\dfrac{23}{7}\\ x=\dfrac{19}{7}\end{matrix}\right.$
`d)|5x-8/9|=0`
`<=>5x-8/9=0`
`<=>5x=0+8/9`
`<=>5x=8/9`
`<=>x=8/9:5`
`<=>x=8/45`
`e)|8/11-x|+4=-2/3`
`<=>|8/11-x|=-2/3-4`
`<=>|8/11-x|=-14/3`
Vì `|8/11-x| ge 0`
Mà `-14/3 <0 =>x` vô nghiệm
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