Đáp án:
`| 5x + 4 | + 7 = 26`
` | 5x + 4 | = 26 - 7 = 19`
⇒\(\left[ \begin{array}{l}5x + 4 = 19\\5x + 4 = -19\end{array} \right.\)
⇒\(\left[ \begin{array}{l}5x =15\\5x =-23\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x = 3\\x = \frac{-23}{5}\end{array} \right.\)
Vậy `x ∈ { 3 ; -23/5}`