Cụ thể, ta có:
+) \(\dfrac{{ - 3}}{5} + \dfrac{1}{2} = \dfrac{{ - 6}}{{10}} + \dfrac{5}{{10}} \)\(= \dfrac{{ - 6 + 5}}{{10}} = \dfrac{{ - 1}}{{10}}\)
+) \(\dfrac{{ - 1}}{4} + \dfrac{{ - 5}}{6} = \dfrac{{ - 3}}{{12}} + \dfrac{{ - 10}}{{12}} \)\(= \dfrac{{ - 3 - 10}}{{12}} = \dfrac{{ - 13}}{{12}}\)
+) \(\dfrac{{ - 3}}{5} + \dfrac{{ - 1}}{4} = \dfrac{{ - 12}}{{20}} + \dfrac{{ - 5}}{{20}} \)\(= \dfrac{{ - 12 - 5}}{{20}} = \dfrac{{ - 17}}{{20}}\)
+) \(\dfrac{1}{2} + \dfrac{{ - 5}}{6} = \dfrac{3}{6} + \dfrac{{ - 5}}{6} = \dfrac{{3 - 5}}{6} \)\(= \dfrac{{ - 2}}{6} = \dfrac{{ - 1}}{3}\)
+) \(\dfrac{{ - 1}}{{10}} + \dfrac{{ - 13}}{{12}} = \dfrac{{ - 6}}{{60}} + \dfrac{{ - 65}}{{60}} \)\(= \dfrac{{ - 6 - 65}}{{60}} = \dfrac{{ - 71}}{{60}}\)
