Đáp án:Giải thích các bước giải:
$\text{A , 3 | x | - 6 = 12}$
$\text{ 3 | x | = 12+6}$
$\text{ 3 | x | = 18}$
$\text{ | x | = 18 : 3 }$
$\text{ | x | = 6}$
$\text{$\Rightarrow$ $\left[\begin{matrix} x=-6\\ x=6\end{matrix}\right.$}$
$\text{Vậy x $\in$ { -6 ; 6 }}$
$\text{B, |3x-1 | - 4 = -4}$
`\text{| 3 x − 1 | = − 4 + 4}`
`\text{| 3 x − 1 | = 0}`
`\text{⇒ 3 x − 1= 0}`
`\text{ 3 x = 0 + 1 }`
`\text{ 3 x = 1}`
`\text{ x = 1 : 3}`
$\text{ x = $\dfrac{1}{3}$}$
$\text{Vậy x = $\dfrac{1}{3}$}$
