Đáp án:
d) x=3
Giải thích các bước giải:
\(\begin{array}{l}
a)\left| {2x - 1} \right| = 5\\
\to \left[ \begin{array}{l}
2x - 1 = 5\\
2x - 1 = - 5
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 3\\
x = - 2
\end{array} \right.\\
b)Do:\left| {7x + 2} \right| \ge 0\forall x\\
\left| {7x + 2} \right| = - 3\left( {voly} \right)\\
\to x \in \emptyset \\
c)\left| {x - 5} \right| = 2x + 1\\
\to \left[ \begin{array}{l}
x - 5 = 2x + 1\left( {DK:x \ge 5} \right)\\
x - 5 = - 2x - 1\left( {DK:x < 5} \right)
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = - 6\left( l \right)\\
3x = 4
\end{array} \right.\\
\to x = \dfrac{4}{3}\\
d)\left| {x + 2} \right| = 4x - 7\\
\to \left[ \begin{array}{l}
x + 2 = 4x - 7\left( {DK:x \ge - 2} \right)\\
x + 2 = - 4x + 7\left( {DK:x < - 2} \right)
\end{array} \right.\\
\to \left[ \begin{array}{l}
3x = 9\\
5x = 5
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 3\\
x = 1\left( l \right)
\end{array} \right.\\
e)\left| {x - 2} \right| = \left| {4x + 7} \right|\\
\to \left[ \begin{array}{l}
x - 2 = 4x + 7\\
x - 2 = - 4x - 7
\end{array} \right.\\
\to \left[ \begin{array}{l}
3x = - 9\\
5x = - 5
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = - 3\\
x = - 1
\end{array} \right.
\end{array}\)
