a. Ta có: \(\dfrac{-1}{3}+\dfrac{-1}{5}+\dfrac{-1}{6}=\dfrac{\left(-10\right)+\left(-6\right)+\left(-5\right)}{30}=\dfrac{-21}{30}\)
Vậy \(\dfrac{-21}{30}=\dfrac{-1}{3}+\dfrac{-1}{5}+\dfrac{-1}{6}\)
b. Ta có: \(\dfrac{-1}{2}+\dfrac{-1}{5}=\dfrac{\left(-5\right)+\left(-2\right)}{10}=\dfrac{-7}{10}\)
Vậy \(\dfrac{-7}{10}=\dfrac{-1}{2}+\dfrac{-1}{5}\)