Đáp án:
Ta có: `|7 - x| ≥ 0 => 5x + 1 ≥ 0 <=> x ≥ \frac{-1}{5}`.
`=>` \(\left[ \begin{array}{l}7-x=5x+1\\7-x=-5x-1\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}7-1=5x+x\\7+1=-5x+x\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}6=6x\\8=-4x\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=1(TM)\\x=-2(KTM)\end{array} \right.\)
Vậy `x = 1`.
Chúc học tốt!!!