Đáp án:
Bài 1:
$a)
x=-10\\
b)
x=\dfrac{-150}{133}\\
c)
x=\dfrac{-2}{3}\\
e)
x=\dfrac{-21}{10}\\
g)
x=\dfrac{-4}{90}\\
h)
x=\dfrac{3}{4}\\
i)
x=\dfrac{-143}{84}$
Giải thích các bước giải:
Bài 1:
$a)
(2,8x-32):\dfrac{2}{3}=-90\\
\Leftrightarrow \dfrac{28}{10}x-32=(-90).\dfrac{2}{3}=-60\\
\Leftrightarrow \dfrac{14}{5}x=-60+32=-28\\
\Leftrightarrow x=(-28).\dfrac{5}{14}\\
\Leftrightarrow x=-10\\
b)
\dfrac{4}{5}+\dfrac{5}{7}:x=\dfrac{1}{6}\\
\Leftrightarrow \dfrac{5}{7}:x=\dfrac{1}{6}-\dfrac{4}{5}\\
\Leftrightarrow \dfrac{5}{7}.\dfrac{1}{x}=\dfrac{5}{30}-\dfrac{24}{30}\\
\Leftrightarrow \dfrac{5}{7}.\dfrac{1}{x}=\dfrac{-19}{30}\\
\Leftrightarrow \dfrac{1}{x}=\dfrac{-19}{30}.\dfrac{7}{5}\\
\Leftrightarrow \dfrac{1}{x}=\dfrac{-133}{150}\\
\Leftrightarrow x=\dfrac{-150}{133}\\
c)
1,5+1\dfrac{1}{4}x=\dfrac{2}{3}\\
\Leftrightarrow \dfrac{3}{2}+\dfrac{5}{4}x=\dfrac{2}{3}\\
\Leftrightarrow \dfrac{5}{4}x=\dfrac{2}{3}-\dfrac{3}{2}\\
\Leftrightarrow \dfrac{5}{4}x=\dfrac{4}{6}-\dfrac{9}{6}\\
\Leftrightarrow \dfrac{5}{4}x=\dfrac{-5}{6}\\
\Leftrightarrow x=\dfrac{-5}{6}.\dfrac{4}{5}=\dfrac{-2}{3}\\
e)
\dfrac{1}{2}x+\dfrac{3}{4}=\dfrac{-3}{10}\\
\Leftrightarrow \dfrac{1}{2}x=\dfrac{-3}{10}-\dfrac{3}{4}\\
\Leftrightarrow \dfrac{1}{2}x=\dfrac{-6}{20}-\dfrac{15}{20}\\
\Leftrightarrow \dfrac{1}{2}x=\dfrac{-21}{20}\\
\Leftrightarrow x=\dfrac{-21}{20}.2=\dfrac{-21}{10}\\
g)
\dfrac{3}{4}x+\dfrac{1}{5}=\dfrac{1}{6}\\
\Leftrightarrow \dfrac{3}{4}x=\dfrac{1}{6}-\dfrac{1}{5}\\
\Leftrightarrow \dfrac{3}{4}x=\dfrac{5}{30}-\dfrac{6}{30}\\
\Leftrightarrow \dfrac{3}{4}x=\dfrac{-1}{30}\\
\Leftrightarrow x=\dfrac{-1}{30}.\dfrac{4}{3}=\dfrac{-4}{90}\\
h)
\dfrac{3}{8}-\dfrac{1}{6}x=\dfrac{1}{4}\\
\Leftrightarrow \dfrac{1}{6}x=\dfrac{3}{8}-\dfrac{1}{4}\\
\Leftrightarrow \dfrac{1}{6}x=\dfrac{3}{8}-\dfrac{2}{8}\\
\Leftrightarrow \dfrac{1}{6}x=\dfrac{1}{8}\\
\Leftrightarrow x=\dfrac{1}{8}.6=\dfrac{3}{4}\\
i)
x+\dfrac{5}{12}=-1\dfrac{2}{7}\\
\Leftrightarrow x=\dfrac{-9}{7}-\dfrac{5}{12}\\
\Leftrightarrow x=\dfrac{-108}{84}-\dfrac{35}{84}\\
\Leftrightarrow x=\dfrac{-143}{84}$
