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a)\(0,5+\dfrac{1}{3}+0,4+\dfrac{5}{7}+\dfrac{1}{6}-\dfrac{4}{35}\)
=\(\left(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}\right)+\left(\dfrac{2}{5}+\dfrac{5}{7}-\dfrac{4}{35}\right)=1+1=2\)
b) \(\dfrac{8}{9}-\dfrac{1}{72}-\dfrac{1}{56}-\dfrac{1}{42}-\dfrac{1}{30}-\dfrac{1}{20}-\dfrac{1}{12}-\dfrac{1}{6}-\dfrac{1}{2}\)
=\(\dfrac{8}{9}-\left(\dfrac{1}{72}+\dfrac{1}{56}+\dfrac{1}{42}+\dfrac{1}{30}+\dfrac{1}{20}+\dfrac{1}{12}+\dfrac{1}{6}+\dfrac{1}{2}\right)\)
=\(\dfrac{8}{9}-\left(\dfrac{1}{8}-\dfrac{1}{9}+\dfrac{1}{7}-\dfrac{1}{8}+...+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{2}\right)=\dfrac{8}{9}-\dfrac{8}{9}=0\)
thế này gọi là gian lận nha
tự đăng tự trả lời thì ko nên đăng làm gì
ko đc gì đâu 
( 2 + \(\dfrac{1}{3}\) - 0,4 ) - ( 7 - \(\dfrac{3}{5}\) - \(\dfrac{4}{3}\)) - ( \(\dfrac{1}{5}\) + \(\dfrac{5}{3}\)- 4)
= 2 + \(\dfrac{1}{3}\)- \(\dfrac{2}{5}\) - 7 + \(\dfrac{3}{5}\) + \(\dfrac{4}{3}\) - \(\dfrac{1}{5}\) - \(\dfrac{5}{3}\) + 4
= ( 2 - 7 + 4) + ( \(\dfrac{1}{3}\) + \(\dfrac{4}{3}\)- \(\dfrac{5}{3}\)) + ( -\(\dfrac{2}{5}\) + \(\dfrac{3}{5}\) - \(\dfrac{1}{5}\))
= -1 + 0 + 0
= - 1
a) \(\dfrac{4}{3}-\left\{\left(6-\dfrac{-11}{6}\right)-\left(\dfrac{2}{9}+\dfrac{5}{3}\right)\right\}\)
\(=\dfrac{4}{3}-\left\{\dfrac{47}{6}-\dfrac{17}{9}\right\}\)
\(=\dfrac{4}{3}-\dfrac{107}{18}\)
\(=\dfrac{-83}{18}\)
b)\(0,5+\dfrac{1}{3}+0,4+\dfrac{5}{7}+\dfrac{1}{6}-\dfrac{1}{35}\)
\(=\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{2}{5}+\dfrac{5}{7}+\dfrac{1}{6}-\dfrac{1}{35}\)
\(=\left(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}\right)+\left(\dfrac{1}{5}+\dfrac{5}{7}-\dfrac{1}{35}\right)\)
\(=1+\dfrac{11}{35}\)
\(=\dfrac{46}{35}\)
\(=\left(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}\right)+\left(\dfrac{2}{5}-\dfrac{4}{35}+\dfrac{5}{7}\right)-\dfrac{1}{41}=-\dfrac{1}{41}\)
\(\dfrac{1}{2}-\dfrac{-2}{5}+\dfrac{1}{3}+\dfrac{5}{7}-\dfrac{-1}{6}+\dfrac{-4}{35}-\dfrac{1}{41}\)
\(=\dfrac{1}{2}+\dfrac{2}{5}+\dfrac{1}{3}+\dfrac{5}{7}+\dfrac{1}{6}+\dfrac{-4}{35}+\dfrac{-1}{41}\)
\(=\left(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}\right)+\left(\dfrac{2}{5}+\dfrac{5}{7}+\dfrac{-4}{35}\right)+\dfrac{-1}{41}\)
\(=1+1+\dfrac{-1}{41}\)
\(=2+\dfrac{-1}{41}=\dfrac{81}{41}\)
\(0,5+\dfrac{1}{3}+0,4+\dfrac{5}{7}+\dfrac{1}{6}-\dfrac{4}{35}+\dfrac{1}{4}\)
\(=\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{2}{5}+\dfrac{5}{7}+\dfrac{1}{6}-\dfrac{4}{35}+\dfrac{1}{4}\)
\(=\left(\dfrac{1}{2}+\dfrac{1}{4}\right)+\left(\dfrac{1}{3}+\dfrac{1}{6}\right)+\left(\dfrac{2}{5}+\dfrac{5}{7}-\dfrac{4}{35}\right)\)
\(=\dfrac{3}{4}+\dfrac{1}{2}+1\)
\(=\dfrac{9}{4}\)
\(0,5+\dfrac{1}{3}+0,4+\dfrac{5}{7}+\dfrac{1}{6}-\dfrac{4}{35}+\dfrac{1}{4}\)
=\(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{2}{5}+\dfrac{5}{7}+\dfrac{1}{6}-\dfrac{4}{35}+\dfrac{1}{4}\)
=\(\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{4}+\dfrac{1}{3}\right)+\left(\dfrac{2}{5}+\dfrac{5}{7}-\dfrac{4}{35}\right)\)
=\(\dfrac{5}{4}+1\)
=\(\dfrac{9}{4}\)