Đáp án:
$a)0\\
b) 0\\
c)
\dfrac{41}{15}\\
d)\dfrac{-11}{10}\\
1)
x=\dfrac{7}{9}\\
2)
x=\dfrac{61}{16}\\
3)
x=\dfrac{-2}{15}\\
4)
x=\dfrac{203}{40}$
Giải thích các bước giải:
$a)\dfrac{-6}{7}.\dfrac{11}{19}-\dfrac{6}{7}.\dfrac{8}{19}+\dfrac{6}{7}\\
=\dfrac{-6}{7}.\left ( \dfrac{11}{19}+\dfrac{8}{19}-1 \right )\\
=\dfrac{-6}{7}.(1-1)\\
=0\\
b) \dfrac{41}{33}+\dfrac{-5}{13}+\dfrac{-8}{13}-\dfrac{8}{33}\\
=\left ( \dfrac{41}{33}-\dfrac{8}{33} \right )+\left ( \dfrac{-5}{13}+\dfrac{-8}{13} \right )\\
=\dfrac{41-8}{33}+\dfrac{-5-8}{13}\\
=1-1=0\\
c)
\dfrac{4}{5}.\dfrac{1}{2}+\dfrac{7}{3}\\
=\dfrac{2}{5}+\dfrac{7}{3}\\
=\dfrac{6}{15}+\dfrac{35}{15}\\
=\dfrac{6+35}{15}=\dfrac{41}{15}\\
d)-2\dfrac{3}{5}+1\dfrac{1}{2}\\
=\dfrac{-13}{5}+\dfrac{3}{2}\\
=\dfrac{(-13).2}{10}+\dfrac{15}{10}\\
=\dfrac{-11}{10}\\
1)
\dfrac{3}{2}x-\dfrac{1}{3}=\dfrac{5}{6}\\
\Leftrightarrow \dfrac{3}{2}x=\dfrac{5}{6}+\dfrac{1}{3}\\
\Leftrightarrow \dfrac{3}{2}x=\dfrac{5}{6}+\dfrac{2}{6}\\
\Leftrightarrow \dfrac{3}{2}x=\dfrac{7}{6}\\
\Leftrightarrow x=\dfrac{7}{6}.\dfrac{2}{3}=\dfrac{7}{9}\\
2)
(2,5-x).\left ( -1\dfrac{1}{7} \right )=\dfrac{3}{2}\\
\Leftrightarrow (\dfrac{25}{10}-x).\dfrac{-8}{7}=\dfrac{3}{2}\\
\Leftrightarrow \dfrac{5}{2}-x=\dfrac{3}{2}.\dfrac{-7}{8}=\dfrac{-21}{16}\\
\Leftrightarrow x=\dfrac{5}{2}+\dfrac{21}{16}\\
\Leftrightarrow x=\dfrac{40}{16}+\dfrac{21}{16}=\dfrac{61}{16}\\
3)
\dfrac{2}{3}-\dfrac{1}{2}.\left ( x+\dfrac{4}{5} \right )=\dfrac{1}{3}\\
\Leftrightarrow \dfrac{1}{2}.\left ( x+\dfrac{4}{5} \right )=\dfrac{2}{3}-\dfrac{1}{3}\\
\Leftrightarrow \dfrac{1}{2}.\left ( x+\dfrac{4}{5} \right )=\dfrac{1}{3}\\
\Leftrightarrow x+\dfrac{4}{5}=\dfrac{1}{3}.2=\dfrac{2}{3}\\
\Leftrightarrow x=\dfrac{2}{3}-\dfrac{4}{5}\\
\Leftrightarrow x=\dfrac{10}{15}-\dfrac{12}{15}\\
\Leftrightarrow x=\dfrac{-2}{15}\\
4)
\dfrac{4}{7}x-\dfrac{2}{5}=1+\dfrac{3}{2}\\
\Leftrightarrow \dfrac{4}{7}x=1+\dfrac{3}{2}+\dfrac{2}{5}\\
\Leftrightarrow \dfrac{4}{7}x=\dfrac{10}{10}+\dfrac{15}{10}+\dfrac{4}{10}\\
\Leftrightarrow \dfrac{4}{7}x=\dfrac{29}{10}\\
\Leftrightarrow x=\dfrac{29}{10}.\dfrac{7}{4}=\dfrac{203}{40}$
