bài 1
\(\dfrac{5}{8}+\dfrac{-13}{8}=\dfrac{5+\left(-13\right)}{8}=\dfrac{-8}{8}=-1\)
\(\dfrac{-4}{13}+\dfrac{22}{-13}\)\(=\dfrac{-4}{13}+\dfrac{-22}{13}=\dfrac{-4+\left(-22\right)}{13}=\dfrac{-26}{13}\)
\(\dfrac{-1}{6}+\dfrac{-13}{15}=\dfrac{-15}{90}+\dfrac{-78}{90}=\dfrac{-15+\left(-78\right)}{90}=\dfrac{-93}{90}\)
\(\dfrac{5}{16}+\dfrac{-5}{24}=\)\(\dfrac{120}{384}+\dfrac{-80}{384}=\dfrac{120+\left(-80\right)}{384}=\dfrac{40}{384}\)
bài 2
\(\dfrac{5}{12}+\dfrac{2}{9}+\dfrac{-7}{12}=\left(\dfrac{5}{12}+\dfrac{-7}{12}\right)+\dfrac{2}{9}=\dfrac{-1}{1}+\dfrac{2}{9}=-1+\dfrac{2}{9}=\dfrac{-9}{9}+\dfrac{2}{9}=\dfrac{-7}{9}\)
\(\dfrac{-7}{19}+\dfrac{2}{11}+\dfrac{-12}{19}=\left(\dfrac{-7}{19}+\dfrac{-12}{19}\right)+\dfrac{2}{11}=\dfrac{-1}{1}+\dfrac{2}{11}=-1+\dfrac{2}{11}=\dfrac{-11}{11}+\dfrac{2}{11}=\dfrac{-9}{11}\)
