`2 ( x + 1 ) | x - 4 | = 0`
`⇔` \(\left[ \begin{array}{l}2 ( x + 1 ) = 0\\| x - 4 | = 0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x + 1 = 2\\x - 4 = 0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x = - 1\\x = 4\end{array} \right.\)
Vậy , `x ∈ { - 1 ; 4 } .`
