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Câu b:
\(\frac{21}{8}:\frac{5}{6}+\frac{1}{2}:\frac{5}{6}\)
= \(\frac{63}{20}+\frac{3}{5}\)
= \(\frac{15}{4}\)
\(\left(\frac{21}{8}+\frac{1}{2}\right):\frac{5}{6}\)
\(\frac{25}{8}:\frac{5}{6}\)
\(\frac{25}{8}.\frac{6}{5}\)
\(\frac{30}{8}\)
a= (\(\frac{2}{5}\)+\(\frac{2}{9}\)+\(\frac{2}{11}\)\(\times\)\(\frac{5}{7}\)\(+\frac{7}{9}\)\(+\frac{7}{11}\)\()\)
Ta có:
\(B=\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)........\left(1-\frac{1}{2017}\right).\left(1-\frac{1}{2018}\right)\)
\(\Rightarrow B=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.......\frac{2016}{2017}.\frac{2017}{2018}\)
Đởn giản hết sẽ còn là:
\(\Rightarrow B=\frac{1}{2018}\)



14 : ( 4\(\frac{2}{3}\)- 1\(\frac{5}{9}\)) + 14 : ( \(\frac{2}{3}\)+ \(\frac{8}{9}\))
= 14 : ( \(\frac{14}{3}\)- \(\frac{14}{9}\)) + 14 : ( \(\frac{6}{9}\) + \(\frac{8}{9}\))
= 14 : ( 14 - \(\frac{14}{9}\)) + 14 : \(\frac{14}{9}\)
= 14 : \(\frac{112}{9}\)+ 14 : \(\frac{14}{9}\)
= \(\frac{9}{8}\)+ 9
= \(\frac{81}{8}\)