Tính nhanh.
a) \(\frac{-3}{7}+\frac{5}{13}+\frac{-4}{7}\) ;
b) \(\frac{-5}{21}+\frac{-2}{21}+\frac{8}{24}\) .
Câu a:
\(\frac{-3}{7}+\frac{5}{13}+\frac{-4}{7}= \frac{-3}{7}+\frac{4}{7}+\frac{5}{13}=-1+\frac{5}{13}\)
\(=\frac{-13}{13}+\frac{5}{13}=\frac{-8}{13}\).
Câu b:
\(\frac{-5}{21}+\frac{-2}{21}+\frac{8}{24}=\frac{-7}{21}+\frac{1}{3}=\frac{-1}{3}+\frac{1}{3}=0\) .
-- Mod Toán 6
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