Đáp án:
d) \(\left[ \begin{array}{l}
x = \dfrac{1}{5}\\
x = - \dfrac{9}{5}
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
B3:\\
a)\dfrac{9}{{20}} - \left| {\dfrac{{13}}{{10}} - x} \right| = 0\\
\to \left| {\dfrac{{13}}{{10}} - x} \right| = \dfrac{9}{{20}}\\
\to \left[ \begin{array}{l}
\dfrac{{13}}{{10}} - x = \dfrac{9}{{20}}\left( {DK:\dfrac{{13}}{{10}} \ge x} \right)\\
\dfrac{{13}}{{10}} - x = - \dfrac{9}{{20}}\left( {DK:\dfrac{{13}}{{10}} < x} \right)
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{{17}}{{20}}\left( {TM} \right)\\
x = \dfrac{7}{4}\left( {TM} \right)
\end{array} \right.\\
b)\left| {3x - 5} \right| - \dfrac{1}{7} = \dfrac{1}{3}\\
\to \left| {3x - 5} \right| = \dfrac{{10}}{{21}}\\
\to \left[ \begin{array}{l}
3x - 5 = \dfrac{{10}}{{21}}\\
3x - 5 = - \dfrac{{10}}{{21}}
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{{115}}{{63}}\\
x = \dfrac{{95}}{{63}}
\end{array} \right.\\
c)\dfrac{x}{{28}} = - \dfrac{4}{7}\\
\to x = - 16\\
d)\left| {x + \dfrac{4}{5}} \right| = 1\\
\to \left[ \begin{array}{l}
x + \dfrac{4}{5} = 1\\
x + \dfrac{4}{5} = - 1
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{1}{5}\\
x = - \dfrac{9}{5}
\end{array} \right.
\end{array}\)
