Lời giải:
`a)|x|=7`
`<=>`\(\left[ \begin{array}{l}x=7\\x=-7\end{array} \right.\)
Vậy `x in {+-7}`
`b)|x+1|=2`
`<=>`\(\left[ \begin{array}{l}x+1=2\\x+1=-2\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=1\\x=-3\end{array} \right.\)
Vậy `x in {1;-3}`
`c)|x-5,1|-3,9=2`
`<=>|x-5,1|=5,9`
`<=>`\(\left[ \begin{array}{l}x-5,1=5,9\\x-5,1=-5,9\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=11\\x=-0,8\end{array} \right.\)
Vậy `x in {11;-0,8}`
`d)|3-2x|-2x=5,3`
`<=>|3-2x|=5,3+2x`
`<=>`\(\left[ \begin{array}{l}3-2x=5,3+2x\\3-2x=-5,3-2x\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}-4x=2,3\\0=-8,3(vô lý)\end{array} \right.\)
`<=>x=-0,575`
Vậy `x=-0,575`
