Bài 5.
a. Ta có: \(\dfrac{1}{-2}=\dfrac{-1}{2}\)
Vì \(2< 3\Rightarrow\dfrac{1}{2}>\dfrac{1}{3}\Rightarrow\dfrac{-1}{2}< \dfrac{-1}{3}\Rightarrow\dfrac{1}{-2}< \dfrac{-1}{3}\)
b. Vì \(-2< 0\Rightarrow\dfrac{-2}{3}< \dfrac{0}{3}\Rightarrow\dfrac{-2}{3}< 0\)
c. Nhận thấy: \(\dfrac{1}{-8}=-0,125\Rightarrow-0,125=\dfrac{1}{-8}\)
Bài 6.
a. Vì \(-5< 2\Rightarrow\dfrac{-5}{43}< \dfrac{2}{43}\)
b. Vì \(3>2\Rightarrow\dfrac{1}{3}< \dfrac{1}{2}\Rightarrow\dfrac{5}{3}< \dfrac{5}{2}\)
c. Ta có: \(\dfrac{-2}{-3}=\dfrac{2}{3},\) \(\dfrac{-2}{-5}=\dfrac{2}{5}\)
Vì \(3< 5\Rightarrow\dfrac{2}{3}>\dfrac{2}{5}\Rightarrow\dfrac{-2}{-3}>\dfrac{-2}{-5}\)
d. Ta có: \(-11>-12\Rightarrow\dfrac{-11}{15}>\dfrac{-12}{15}\)
e. Ta có: \(7>-12\Rightarrow\dfrac{1}{7}< \dfrac{1}{-12}\Rightarrow\dfrac{-5}{7}>\dfrac{-5}{-12}\)
