Đáp án:
$1)
a)x=\dfrac{11}{8}\\
b)
x=\dfrac{5}{3}\\
2)
a) x=7\\
b){\left[\begin{aligned}x=11\\x=-1\end{aligned}\right.}\\$
Giải thích các bước giải:
$1)
a)\dfrac{7}{5}-\dfrac{2}{5}x=1-\dfrac{3}{20}\\
\Leftrightarrow \dfrac{2}{5}x=\dfrac{7}{5}-1+\dfrac{3}{20}\\
\Leftrightarrow \dfrac{2}{5}x=\dfrac{28}{20}-\dfrac{20}{20}+\dfrac{3}{20}\\
\Leftrightarrow \dfrac{2}{5}x=\dfrac{11}{20}\\
\Leftrightarrow x=\dfrac{11}{20}.\dfrac{5}{2}=\dfrac{11}{8}\\
b)
\dfrac{2}{5}x+\dfrac{-3}{7}=\dfrac{-1}{5}x+\dfrac{8}{14}\\
\Leftrightarrow \dfrac{2}{5}x+\dfrac{1}{5}x=\dfrac{8}{14}+\dfrac{3}{7}\\
\Leftrightarrow \dfrac{2}{5}x+\dfrac{1}{5}x=\dfrac{4}{7}+\dfrac{3}{7}\\
\Leftrightarrow \dfrac{3}{5}x=\dfrac{7}{7}=1\\
\Leftrightarrow x=\dfrac{5}{3}\\
2)
a)(-4)-2x=(-3).6\\
\Leftrightarrow 2x=-4+18=14\\
\Leftrightarrow x=7\\
b)\dfrac{-3}{4}.|x-5|=\dfrac{-9}{2}\\
\Leftrightarrow |x-5|=\dfrac{-9}{2}.\dfrac{-4}{3}=6\\
\Leftrightarrow {\left[\begin{aligned}x-5=6\\x-5=-6\end{aligned}\right.}\\
\Leftrightarrow {\left[\begin{aligned}x=11\\x=-1\end{aligned}\right.}\\$
