Đáp án:
`k.`
`|x|=5`
`x=+-5`
`l.`
`|x – 3| = 1`
$\left[\begin{matrix} x-3=1\\ x-3=-1\end{matrix}\right.$
$\left[\begin{matrix} x=4\\ x=2\end{matrix}\right.$
`m.`
`|x + 2| = 4`
$\left[\begin{matrix} x+2=4\\ x+2=-4\end{matrix}\right.$
$\left[\begin{matrix} x=2\\ x=-6\end{matrix}\right.$
`n.`
`3 - |2x +1| = (-5)`
` - |2x+1|=-5 - 3`
` - |2x+1|=-8`
` |2x+1|=8`
$\left[\begin{matrix} 2x+1=8\\ 2x+1=-8\end{matrix}\right.$
$\left[\begin{matrix} x=7/2\\ x=-9/2\end{matrix}\right.$
`o`
`12 + |3 - x| = 9`
`|3 - x| = 9-12`
`|3 - x| = -3`
$\left[\begin{matrix} 3 - x=-3\\ 3 - x=3\end{matrix}\right.$
$\left[\begin{matrix} x=6\\ x=0\end{matrix}\right.$
`p.`
`|x + 9| = 12 + (-9) + 2`
`|x+9|=5`
$\left[\begin{matrix} x+9=5\\ x+9=-5\end{matrix}\right.$
$\left[\begin{matrix} x=-4\\ x=-14\end{matrix}\right.$
`q.`
`|x + 5| - 5 = 4 - (-3)`
`|x + 5| - 5 = 7`
`|x + 5| =7+5`
`|x + 5| = 12`
$\left[\begin{matrix} x + 5=12\\ x + 5=-12\end{matrix}\right.$
$\left[\begin{matrix} x=7\\ x=-17\end{matrix}\right.$
`h.`
`-|-5| - (-x) + 4 = 3 -(-25)`
`-5 +x + 4=28`
`x+4=28+5`
`x+4=33`
`x=29`
