Đáp án:
$c) \dfrac{239}{540}\\
2)
a)x=\dfrac{6}{7}\\
b) x=\dfrac{-2}{5}\\
c)
x=\dfrac{-1}{3}$
Giải thích các bước giải:
$ c)\dfrac{-14}{5}.\dfrac{5}{8}+\dfrac{-4}{15}.\dfrac{-13}{18}+|-2|\\
=\dfrac{-7}{4}+\dfrac{26}{135}+2\\
=\dfrac{(-7).135}{4.135}+\dfrac{26.4}{135.4}+\dfrac{2.540}{540}\\
=\dfrac{239}{540}\\
2)
a)\dfrac{3}{5}+\dfrac{2}{5}:x=1\dfrac{1}{15}\\
\Leftrightarrow \dfrac{2}{5}.\dfrac{1}{x}=\dfrac{16}{15}-\dfrac{3}{5}\\
\Leftrightarrow \dfrac{2}{5}.\dfrac{1}{x}=\dfrac{16}{15}-\dfrac{9}{15}\\
\Leftrightarrow \dfrac{2}{5}.\dfrac{1}{x}=\dfrac{7}{15}\\
\Leftrightarrow \dfrac{1}{x}=\dfrac{7}{15}.\dfrac{5}{2}=\dfrac{7}{6}\\
\Leftrightarrow x=\dfrac{6}{7}\\
b) \dfrac{4}{5}-\dfrac{1}{2}x=1\\
\Leftrightarrow \dfrac{1}{2}x=\dfrac{4}{5}-1\\
\Leftrightarrow \dfrac{1}{2}x=\dfrac{4}{5}-\dfrac{5}{5}
\Leftrightarrow \dfrac{1}{2}x=\dfrac{-1}{5}\\
\Leftrightarrow x=\dfrac{-1}{5}.2=\dfrac{-2}{5}\\
c)
(3x+2)^3=2020^0\\
\Leftrightarrow (3x+2)^3=1\\
\Leftrightarrow 3x+2=1\\
\Leftrightarrow 3x=1-2=-1\\
\Leftrightarrow x=\dfrac{-1}{3}$
