Question

Answer 1

Bài 1: 

a) \(\dfrac{-5}{13}+\dfrac{-7}{13}=\dfrac{-5-7}{13}=\dfrac{-12}{13}\)

b) \(\dfrac{-3}{14}+\dfrac{2}{21}=\dfrac{-9}{42}+\dfrac{4}{42}=\dfrac{-5}{42}\)

c) \(\dfrac{1313}{1515}+\dfrac{-1011}{5055}=\dfrac{13}{15}-\dfrac{1}{5}=\dfrac{13}{15}-\dfrac{3}{15}=\dfrac{10}{15}=\dfrac{2}{3}\)

Answer 2

Bài 2: 

a) \(\dfrac{2}{15}-\dfrac{7}{10}=\dfrac{4}{30}-\dfrac{21}{30}=\dfrac{-17}{30}\)

b) \(-5-\dfrac{2}{7}=\dfrac{-35}{7}-\dfrac{2}{7}=\dfrac{-37}{7}\)

c) \(2.5-\left(-\dfrac{3}{4}\right)=\dfrac{5}{2}+\dfrac{3}{4}=\dfrac{10}{4}+\dfrac{3}{4}=\dfrac{14}{4}\)