Tính giá trị biểu thức a) 2/3 + 2/5 - 2/9 / 4/3 + 4/5 - 4/9 b) 3/4 + 3/7

* Hướng dẫn giải

a) $\frac{\frac{2}{3}+\frac{2}{5}-\frac{2}{9}}{\frac{4}{3}+\frac{4}{5}-\frac{4}{9}}=\frac{2\left(\frac{1}{3}+\frac{1}{5}-\frac{1}{9}\right)}{4\left(\frac{1}{3}+\frac{1}{5}-\frac{1}{9}\right)}=\frac{1}{2}$

b) $\frac{\frac{3}{4}+\frac{3}{7}-\frac{3}{8}}{\frac{5}{4}+\frac{5}{7}-\frac{5}{8}}+1=\frac{3\left(\frac{1}{4}+\frac{1}{7}-\frac{1}{8}\right)}{5\left(\frac{1}{4}+\frac{1}{7}-\frac{1}{8}\right)}+1=\frac{3}{5}+1=\frac{8}{5}$