Bài 6:
a: \(\dfrac{-4}{5}+\dfrac{6}{7}\)
\(=\dfrac{-4\cdot7+6\cdot5}{35}\)
\(=\dfrac{2}{35}\)
b: \(\dfrac{-2}{21}-\dfrac{5}{-24}\)
\(=\dfrac{-2}{21}+\dfrac{5}{24}\)
\(=\dfrac{-2\cdot8+5\cdot7}{168}=\dfrac{19}{168}\)
c: \(\dfrac{7}{15}-\dfrac{-8}{25}+\dfrac{11}{-75}\)
\(=\dfrac{7}{15}+\dfrac{8}{25}-\dfrac{11}{75}\)
\(=\dfrac{7\cdot5+8\cdot3-11}{75}\)
\(=\dfrac{48}{75}=\dfrac{16}{25}\)
Bài 5:
a: \(\dfrac{2}{5}+\dfrac{3}{4}:x=-\dfrac{1}{2}\)
=>\(\dfrac{3}{4}:x=-\dfrac{1}{2}-\dfrac{2}{5}\)
=>\(\dfrac{3}{4}:x=\dfrac{-5-4}{10}=\dfrac{-9}{10}\)
=>\(x=-\dfrac{3}{4}:\dfrac{9}{10}=\dfrac{-3}{4}\cdot\dfrac{10}{9}=\dfrac{-30}{36}=\dfrac{-5}{6}\)
b: \(x:\dfrac{46}{95}=\dfrac{20}{23}\)
=>\(x=\dfrac{20}{23}\cdot\dfrac{46}{95}\)
=>\(x=\dfrac{20}{95}\cdot\dfrac{46}{23}\)
=>\(x=\dfrac{4}{19}\cdot2=\dfrac{8}{19}\)
c: \(\dfrac{-85}{33}:x=\dfrac{-25}{11}\)
=>\(\dfrac{85}{33}:x=\dfrac{25}{11}\)
=>\(x=\dfrac{85}{33}:\dfrac{25}{11}=\dfrac{85}{33}\cdot\dfrac{11}{25}=\dfrac{11}{33}\cdot\dfrac{85}{25}=\dfrac{17}{5}\cdot\dfrac{1}{3}=\dfrac{17}{15}\)
Bài 5 :
a) \(\dfrac{2}{5}+\dfrac{3}{4}:x=-\dfrac{1}{2}\)
\(\dfrac{3}{4}:x=-\dfrac{1}{2}-\dfrac{2}{5}\)
\(\dfrac{3}{4}:x=-\dfrac{9}{10}\)
\(x=\dfrac{3}{4}:-\dfrac{9}{10}\)
\(x=-\dfrac{5}{6}\)
b)\(x:\dfrac{46}{95}=\dfrac{20}{33}\)
\(x=\dfrac{20}{23}.\dfrac{46}{95}\)
x = 8/19
c)\(-\dfrac{85}{33}:x=\dfrac{25}{-11}\)
\(x=-\dfrac{85}{33}:\dfrac{25}{-11}\)
\(x=\dfrac{17}{15}\)
Zzz 💢
