Đáp án:
g) \(\left[ \begin{array}{l}
x = 4\\
x = - \dfrac{{16}}{5}
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a)\dfrac{2}{3}x + \dfrac{5}{7} = \dfrac{5}{{10}}\\
\to \dfrac{2}{3}x = \dfrac{5}{{10}} - \,\dfrac{5}{7}\\
\to \dfrac{2}{3}x = - \dfrac{3}{{14}}\\
\to x = - \dfrac{9}{{28}}\\
b) - \dfrac{{21}}{{13}}x = \dfrac{2}{3} - \dfrac{1}{3}\\
\to - \dfrac{{21}}{{13}}x = \dfrac{1}{3}\\
\to x = - \dfrac{{13}}{{63}}\\
c)\dfrac{3}{7}x + \dfrac{{19}}{8} = \dfrac{7}{5}\\
\to \dfrac{3}{7}x = \dfrac{7}{5} - \dfrac{{19}}{8}\\
\to \dfrac{3}{7}x = - \dfrac{{39}}{{40}}\\
\to x = - \dfrac{{91}}{{40}}\\
d)\dfrac{1}{{7x}} = \dfrac{3}{{14}} - \dfrac{3}{7}\\
\to \dfrac{1}{{7x}} = - \dfrac{3}{{14}}\\
\to x = - \dfrac{3}{2}\\
e)\left| {x - \dfrac{2}{5}} \right| = \dfrac{1}{4}\\
\to \left[ \begin{array}{l}
x - \dfrac{2}{5} = \dfrac{1}{4}\\
x - \dfrac{2}{5} = - \dfrac{1}{4}
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{{13}}{{20}}\\
x = \dfrac{3}{{20}}
\end{array} \right.\\
f)\left| {x + \dfrac{1}{2}} \right| = \dfrac{{39}}{{10}}\\
\to \left[ \begin{array}{l}
x + \dfrac{1}{2} = \dfrac{{39}}{{10}}\\
x + \dfrac{1}{2} = - \dfrac{{39}}{{10}}
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{{17}}{5}\\
x = - \dfrac{{22}}{5}
\end{array} \right.\\
g)\left| {x - \dfrac{2}{5}} \right| = \dfrac{{18}}{5}\\
\to \left[ \begin{array}{l}
x - \dfrac{2}{5} = \dfrac{{18}}{5}\\
x - \dfrac{2}{5} = - \dfrac{{18}}{5}
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 4\\
x = - \dfrac{{16}}{5}
\end{array} \right.
\end{array}\)
