Đáp án:
a) \(\left[ \begin{array}{l}
A = - 3x + 4\\
A = 7x - 6
\end{array} \right.\)
b) \(\left[ \begin{array}{l}
x = \dfrac{1}{3}\\
x = \dfrac{9}{7}
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a)A = \left| {x + 1} \right| + \left| {4 - 6x} \right| + 2x - 1\\
\to \left[ \begin{array}{l}
A = x + 1 + 4 - 6x + 2x - 1\left( {DK:\dfrac{2}{3} \ge x \ge - 1} \right)\\
A = - x - 1 - 4 + 6x + 2x - 1\left( {DK:\left[ \begin{array}{l}
x > \dfrac{2}{3}\\
x < - 1
\end{array} \right.} \right)
\end{array} \right.\\
\to \left[ \begin{array}{l}
A = - 3x + 4\\
A = 7x - 6
\end{array} \right.\\
b)A = 3\\
\to \left[ \begin{array}{l}
- 3x + 4 = 3\\
7x - 6 = 3
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{1}{3}\left( {TM} \right)\\
x = \dfrac{9}{7}\left( {TM} \right)
\end{array} \right.
\end{array}\)
