Đáp án:
$14)
a)
x=-2\\
b)
x=-1\\$
Giải thích các bước giải:
$14)
a)
\left ( \dfrac{3x}{7}+1 \right ):-4=\dfrac{-1}{28}\\
\Leftrightarrow \dfrac{3}{7}x+1=\dfrac{-1}{28}.(-4)\\
\Leftrightarrow \dfrac{3}{7}x=\dfrac{1}{7}-1\\
\Leftrightarrow \dfrac{3}{7}x=\dfrac{1}{7}-\dfrac{7}{7}=\dfrac{-6}{7}\\
\Leftrightarrow x=\dfrac{-6}{7}.\dfrac{7}{3}\\
\Leftrightarrow x=-2\\
b)
\left ( 3\dfrac{1}{2}-2x \right ).1\dfrac{1}{3}=7\dfrac{1}{3}\\
\Leftrightarrow \left ( \dfrac{7}{2}-2x \right ).\dfrac{4}{3}=\dfrac{22}{3}\\
\Leftrightarrow \dfrac{7}{2}-2x =\dfrac{22}{3}.\dfrac{3}{4}=\dfrac{11}{2}\\
\Leftrightarrow 2x=\dfrac{7}{2}-\dfrac{11}{2}=-2\\
\Leftrightarrow x=-1\\$
