Đáp án:
g) \(\left[ \begin{array}{l}
x = 2\\
x = - 6
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a)\dfrac{{30}}{{40}} = \dfrac{x}{8}\\
\to \dfrac{x}{8} = \dfrac{3}{4}\\
\to x = \dfrac{3}{4}.8\\
\to x = 6\\
b)\dfrac{3}{5}x - \dfrac{1}{2} = - \dfrac{1}{7}\\
\to \dfrac{3}{5}x = - \dfrac{1}{7} + \dfrac{1}{2}\\
\to \dfrac{3}{5}x = \dfrac{5}{{14}}\\
\to x = \dfrac{5}{{14}}:\dfrac{3}{5}\\
\to x = \dfrac{{25}}{{42}}\\
c)x.\dfrac{5}{3} + \dfrac{1}{4} = \dfrac{4}{9}\\
\to x.\dfrac{5}{3} = \dfrac{7}{{36}}\\
\to x = \dfrac{7}{{36}}:\dfrac{5}{3}\\
\to x = \dfrac{7}{{60}}\\
d)12 - 3\left| x \right| = 6\\
\to 3\left| x \right| = 6\\
\to \left| x \right| = 2\\
\to \left[ \begin{array}{l}
x = 2\\
x = - 2
\end{array} \right.\\
e)\left| {x - \dfrac{3}{2}} \right| = 2\\
\to \left[ \begin{array}{l}
x - \dfrac{3}{2} = 2\\
x - \dfrac{3}{2} = - 2
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{7}{2}\\
x = - \dfrac{1}{2}
\end{array} \right.\\
g)4\left| {x + 2} \right| = 16\\
\to \left| {x + 2} \right| = 4\\
\to \left[ \begin{array}{l}
x + 2 = 4\\
x + 2 = - 4
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 2\\
x = - 6
\end{array} \right.
\end{array}\)
