Question

So sánh phân số: 

a) \(\dfrac{-15}{17}\)và\(\dfrac{-19}{21}\)                          c) \(\dfrac{-317}{633}\)và \(\dfrac{-371}{743}\)

b)\(\dfrac{-23}{49}\)và \(\dfrac{-25}{47}\)                          d) \(\dfrac{-24}{35}\) và \(\dfrac{-19}{30}\)

 

Answer 1

\(a,\dfrac{-15}{17}=-1+\dfrac{2}{17}\\ -\dfrac{19}{21}=-1+\dfrac{2}{21}\\ Vì:\dfrac{2}{17}>\dfrac{2}{21}\Rightarrow-1+\dfrac{2}{17}>-1+\dfrac{2}{21}\Rightarrow-\dfrac{15}{17}>-\dfrac{19}{21}\\ b,-\dfrac{24}{35}=-1+\dfrac{11}{35};-\dfrac{19}{30}=-1+\dfrac{11}{30}\\ Vì:\dfrac{11}{35}< \dfrac{11}{30}\Rightarrow-1+\dfrac{11}{35}< -1+\dfrac{11}{30}\\ \Rightarrow-\dfrac{24}{35}< -\dfrac{19}{30}\)