Đáp án:
$2)
a) x=\dfrac{-2}{3}\\
b)
x=\dfrac{-1}{5}\\
c)
{\left[\begin{aligned}x=\dfrac{8}{7}\\x=\dfrac{-4}{7}\end{aligned}\right.}\\$
Giải thích các bước giải:
$2)
a) \left ( 3x-2^4 \right ).7^3=2.7^4\\
\Leftrightarrow 3x-2^4=\dfrac{2.7^4}{7^3}=2.7=14\\
\Leftrightarrow 3x=14-2^4=-2\\
\Leftrightarrow x=\dfrac{-2}{3}\\
b)
\dfrac{2}{3}+\dfrac{1}{3}:x=-1\\
\Leftrightarrow \dfrac{1}{3}.\dfrac{1}{x}=-1-\dfrac{2}{3}\\
\Leftrightarrow \dfrac{1}{3}.\dfrac{1}{x}=-\dfrac{3}{3}-\dfrac{2}{3}\\
\Leftrightarrow \dfrac{1}{3}.\dfrac{1}{x}=\dfrac{-5}{3}\\
\Leftrightarrow \dfrac{1}{x}=\dfrac{-5}{3}.3=-5\\
\Leftrightarrow x=\dfrac{-1}{5}\\
c)
\left | x-\dfrac{2}{7} \right |=\dfrac{-15}{14}.\dfrac{4}{-5}\\
\Leftrightarrow \left | x-\dfrac{2}{7} \right |=\dfrac{3}{7}.\dfrac{2}{1}\\
\Leftrightarrow \left | x-\dfrac{2}{7} \right |=\dfrac{6}{7}\\
\Leftrightarrow {\left[\begin{aligned}x-\dfrac{2}{7}=\dfrac{6}{7}\\x-\dfrac{2}{7}=\dfrac{-6}{7}\end{aligned}\right.}\\
\Leftrightarrow {\left[\begin{aligned}x=\dfrac{6}{7}+\dfrac{2}{7}\\x=\dfrac{-6}{7}+\dfrac{2}{7}\end{aligned}\right.}\\
\Leftrightarrow {\left[\begin{aligned}x=\dfrac{8}{7}\\x=\dfrac{-4}{7}\end{aligned}\right.}\\$
