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Bài 1 :
\(a,\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-1\frac{7}{21}+2\)
\(=\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{7}{21}-1\frac{7}{21}\right)+2\)
\(=1-1+2\)
\(=2\)
Học tốt
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có: \(\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-\frac{36}{21}+\frac{2}{3}\)
\(=\frac{15}{34}+\frac{19}{34}+\frac{7}{21}-\frac{36}{21}+\frac{2}{3}\)
\(=1-\frac{29}{31}+\frac{2}{3}=\frac{2}{31}+\frac{2}{3}=\frac{68}{93}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{\left(\frac{3}{10}-\frac{4}{15}-\frac{7}{20}\right).\frac{5}{19}}{\left(\frac{1}{14}+\frac{1}{7}-\frac{-3}{35}\right).\frac{-4}{3}}=\frac{\left(\frac{18}{60}-\frac{16}{60}-\frac{21}{60}\right).\frac{5}{19}}{\left(\frac{5}{70}+\frac{7}{70}-\frac{-6}{70}\right).\frac{-4}{3}}\)
\(=\frac{-\frac{19}{60}.\frac{5}{19}}{\frac{3}{10}.\frac{-4}{3}}=\frac{-\frac{1}{12}}{-\frac{2}{5}}=\frac{5}{24}\)
dễ quá bạn ơi