tính 1/5+4/11+4/5+7/11

* Hướng dẫn giải

$$\begin{gathered} a) \frac{1}{5}+\frac{4}{11}+\frac{4}{5}+\frac{7}{11}=(\frac{1}{5}+\frac{4}{5})+(\frac{4}{11}+\frac{7}{11}) \\ = 1+1=2 \\ b) \frac{5}{6}+(\frac{5}{9}-\frac{1}{4})=\frac{5}{6}+\frac{20}{36}-\frac{9}{39} \\ =\frac{5}{6}+\frac{11}{36}=\frac{30}{36}+\frac{11}{36}=\frac{41}{36} \end{gathered}$$