\(\dfrac{2}{5}+\left(-\dfrac{4}{3}\right)+\left(-\dfrac{1}{2}\right)\)

\(=\dfrac{2}{5}-\dfrac{4}{3}-\dfrac{1}{2}\)

\(=\dfrac{6}{15}-\dfrac{20}{15}-\dfrac{1}{2}\)

\(=\dfrac{-14}{15}-\dfrac{1}{2}\)

\(=\dfrac{-28}{30}-\dfrac{15}{30}\)

\(=\dfrac{-43}{30}\)

cách làm bài này đây nha bạn

câu 1

\(-\dfrac{5}{6}-\left(-\dfrac{3}{8}+\dfrac{1}{10}\right)\)

\(=-\dfrac{5}{6}+\dfrac{3}{8}-\dfrac{1}{10}\)

\(=\dfrac{-40}{48}+\dfrac{18}{48}-\dfrac{1}{10}\)

\(=\dfrac{-22}{48}-\dfrac{1}{10}\)

\(=\dfrac{-11}{24}-\dfrac{1}{10}\)

\(=\dfrac{-110}{240}-\dfrac{24}{240}\)

\(=\dfrac{-134}{240}\)

\(=\dfrac{-67}{120}\)

\(-1,75-\left(-\dfrac{1}{9}-2\dfrac{1}{18}\right)\)

\(=\dfrac{-175}{100}+\dfrac{1}{9}+2\dfrac{1}{18}\)

\(=\dfrac{-7}{4}+\dfrac{1}{9}+\dfrac{37}{18}\)

\(=\dfrac{-63}{36}+\dfrac{4}{36}+\dfrac{74}{36}\)

\(=\dfrac{-59}{36}+\dfrac{74}{36}\)

\(=\dfrac{15}{36}\)

\(=\dfrac{-19}{8}\)

\(\dfrac{-1}{12}-\left(2\dfrac{5}{8}-\dfrac{1}{3}\right)\)

\(=\dfrac{-1}{12}-2\dfrac{5}{8}+\dfrac{1}{3}\)

\(=\dfrac{-1}{12}+\dfrac{-21}{8}+\dfrac{1}{3}\)

\(=\dfrac{-8}{96}+\dfrac{-252}{96}+\dfrac{1}{3}\)

\(=\dfrac{-260}{96}+\dfrac{1}{3}\)

\(=\dfrac{-65}{24}+\dfrac{1}{3}\)

\(=\dfrac{-65}{24}+\dfrac{8}{24}\)

\(=\dfrac{-57}{24}\)

bài 2)

a)\(\dfrac{-7}{2}+\dfrac{3}{4}-\dfrac{17}{12}\)

\(=\dfrac{-42}{12}+\dfrac{9}{12}-\dfrac{17}{12}\)

\(=\dfrac{-33}{12}-\dfrac{17}{12}\)

\(=\dfrac{-50}{12}\)

\(=\dfrac{-25}{6}\)

b)\(-\dfrac{5}{6}-\left(-\dfrac{3}{8}+\dfrac{1}{10}\right)\)

\(=-\dfrac{5}{6}+\dfrac{3}{8}-\dfrac{1}{10}\)

\(=-\dfrac{40}{48}+\dfrac{18}{48}-\dfrac{1}{10}\)

\(=\dfrac{-22}{48}-\dfrac{1}{10}\)

\(=\dfrac{-11}{24}-\dfrac{1}{10}\)

\(=\dfrac{-110}{240}-\dfrac{24}{240}\)

\(=\dfrac{-134}{240}\)

\(=\dfrac{-67}{120}\)

bài 1)

c)\(\dfrac{-2}{5}-\dfrac{-3}{11}\)

\(=\dfrac{-2}{5}+\dfrac{3}{11}\)

\(=\dfrac{-22}{55}+\dfrac{15}{55}\)

\(=\dfrac{-7}{55}\)

d)\(\dfrac{-5}{12}+0,75\)

\(=\dfrac{-5}{12}+\dfrac{75}{100}\)

\(=\dfrac{-5}{12}+\dfrac{3}{4}\)

\(=\dfrac{-5}{12}+\dfrac{9}{12}\)

\(=\dfrac{4}{12}\)

\(=\dfrac{1}{3}\)

c)\(\dfrac{5}{7}.12\dfrac{1}{2}-\dfrac{5}{7}.5\dfrac{1}{2}\)

\(=\dfrac{5}{7}\left(12\dfrac{1}{2}-5\dfrac{1}{2}\right)\)

\(=\dfrac{5}{7}.7\)

\(=\dfrac{35}{7}\)

\(=5\)