Đề bài

Thay dấu ? bằng dấu >, <, = thích hợp.

a) $\left( {\dfrac{{ - 4}}{9}} \right) + \left( {\dfrac{5}{{ - 9}}} \right)$ ?  -1

b) $\left( {\dfrac{{ - 13}}{{33}}} \right) + \left( {\dfrac{{ - 14}}{{33}}} \right)$ ? $\dfrac{{ - 10}}{{11}}$

c) $\dfrac{1}{5} + \left( {\dfrac{{ - 2}}{3}} \right)$ ? $\dfrac{2}{5} + \left( {\dfrac{{ - 4}}{5}} \right)$