Đáp án:
$a)
\dfrac{-391}{154}\\
b)
\dfrac{-1}{9}\\
c)
x=-1$
Giải thích các bước giải:
$a)
\dfrac{-5}{7}.\dfrac{5}{11}+\dfrac{-5}{7}:\dfrac{2}{11}+1\dfrac{5}{7}\\
=\dfrac{-5}{7}.\dfrac{5}{11}+\dfrac{-5}{7}.\dfrac{11}{2}+\dfrac{12}{7}\\
=\dfrac{-5}{7}.\left ( \dfrac{5}{11}+\dfrac{11}{2} \right )+\dfrac{12}{7}\\
=\dfrac{-5}{7}.\left ( \dfrac{10}{22}+\dfrac{11.11}{22} \right )+\dfrac{12}{7}\\
=\dfrac{-5}{7}.\dfrac{131}{22}+\dfrac{12}{7}\\
=\dfrac{1}{7}.\left ( \dfrac{-655}{22}+\dfrac{12.22}{22} \right )\\
=\dfrac{1}{7}.\dfrac{-391}{22}\\
=\dfrac{-391}{154}\\
b)
\dfrac{-1}{3}+\dfrac{1}{3}.\left ( \dfrac{-4}{9}+\dfrac{5}{6} \right ):\dfrac{7}{12}\\
=\dfrac{-1}{3}+\dfrac{1}{3}.\left ( \dfrac{-4.2}{18}+\dfrac{5.3}{18} \right ).\dfrac{12}{7}\\
=\dfrac{-1}{3}+\dfrac{1}{3}.\dfrac{7}{18}.\dfrac{12}{7}\\
=\dfrac{1}{3}.\left ( -1+\dfrac{12}{18} \right )\\
=\dfrac{1}{3}.\left ( \dfrac{-3}{3}+\dfrac{2}{3} \right )\\
=\dfrac{1}{3}.\dfrac{-1}{3}\\
=\dfrac{-1}{9}\\
c)
\left ( 1\dfrac{1}{3}-\dfrac{25}{100}-\dfrac{5}{12} \right )-2x=1,6:\dfrac{3}{5}\\
\Leftrightarrow \left ( \dfrac{4}{3}-\dfrac{1}{4}-\dfrac{5}{12} \right )-2x=\dfrac{16}{10}.\dfrac{5}{3}\\
\Leftrightarrow \left ( \dfrac{16}{12}-\dfrac{3}{12}-\dfrac{5}{12} \right )-2x=\dfrac{8}{5}.\dfrac{5}{3}\\
\Leftrightarrow \dfrac{8}{12}-2x=\dfrac{8}{3}\\
\Leftrightarrow 2x=\dfrac{2}{3}-\dfrac{8}{3}\\
\Leftrightarrow 2x=\dfrac{-6}{3}=-2\\
\Leftrightarrow x=-1$
