a) \(\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{4}{-9}+\frac{7}{15}\) = \((\frac{-5}{9}+\frac{-4}{9})+\frac{-2}{11}+(\frac{8}{15}+\frac{7}{15})\)

= \(\frac{-9}{9}+\frac{-2}{11}+\frac{15}{15}\)

=\(-1+1+\frac{-2}{11}\)\(\)\(\)

=\(0+\frac{-2}{11}\)

=\(\frac{-2}{11}\)

b)\((\frac72.\frac56)+(\frac76:\frac27)\) = \((\frac72.\frac56)+(\frac76.\frac72)\)

= \(\frac72.\frac{12}{6}\)

= \(\frac72.2\)

= \(\frac{14}{2}\)

= 7

a) \(\frac{5}{-12}\) = \(\frac{-5}{12}\)

BCNN ( 8; 12 ) = 24

24 : 8 = 3 ; 24 : 12 = 2

\(\frac{-3}{8}\) = \(\frac{-3*3}{8*3}\) = \(\frac{-9}{24}\) ; \(\frac{-5}{12}\) = \(\frac{-5*2}{12*2}\) = \(\frac{-10}{24}\)

Vì \(\frac{-9}{24}\) > \(\frac{-10}{24}\) nên \(\frac{-3}{8}\) = \(\frac{5}{-12}\)

b) ƯCLN ( 3131; 5252 ) = 101

\(\frac{3131}{5252}\) = \(\frac{3131:101}{5252:101}\) = \(\frac{31}{52}\)

Vậy \(\frac{3131}{5252}\) = \(\frac{31}{52}\)

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