Bài 1:
a) \(-\frac{3}{7}+\frac{15}{26}-\left(\frac{2}{13}-\frac{3}{7}\right)\)
\(=-\frac{3}{7}+\frac{15}{26}-\frac{4}{26}+\frac{3}{7}\)
\(=\left(-\frac{3}{7}+\frac{3}{7}\right)+\left(\frac{15}{26}-\frac{4}{26}\right)\)
\(=0+\frac{11}{26}\)
\(=\frac{11}{26}\)
b)\(2\frac{3}{7}+\frac{2}{9}-1\frac{3}{7}\)
\(=\frac{17}{7}+\frac{2}{9}-\frac{10}{7}\)
\(=\left(\frac{17}{7}-\frac{10}{7}\right)+\frac{2}{9}\)
\(=1+\frac{2}{9}\)
\(=1\frac{2}{9}=\frac{11}{9}\)
c)\(\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).\left(\frac{1}{6}-\frac{1}{8}-\frac{1}{24}\right)\)
\(=\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).\left(\frac{4}{24}-\frac{3}{24}-\frac{1}{24}\right)\)
\(=\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).0\)
\(=0\)
\(B1:\) \(a,\frac{-3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}\)
= \(\left(\frac{15}{26}-\frac{2}{13}\right)+\left(\frac{3}{7}+\frac{-3}{7}\right)\)
= \(\frac{11}{26}+0=\frac{11}{26}\)
\(b,2\frac{3}{7}-1\frac{3}{7}+\frac{2}{9}\)
= \(1+\frac{2}{9}=1\frac{2}{9}\)
\(c,\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).\left(\frac{4}{24}-\frac{3}{24}-\frac{1}{24}\right)\)
= \(\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).0=0\)
\(B2:\)\(a,\frac{1}{2}.\left(\frac{2}{9}+\frac{3}{12}-\frac{5}{27}\right)\)
= \(\frac{1}{2}.\left(\frac{17}{36}-\frac{5}{27}\right)\)
= \(\frac{1}{2}.\left(\frac{31}{108}\right)\)
= \(\frac{31}{216}\)
b, \(\left(1\frac{4}{5}\right):-3\frac{9}{20}\)
= \(\frac{-12}{23}\)
c, \(\frac{5}{21}-2\frac{11}{14}\)
= \(-2\frac{23}{42}\)
d, \(70\frac{1}{2}-70\frac{2}{5}\)
= \(1\frac{1}{704}\)
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