Ta có: \(\dfrac{4}{9}+\dfrac{6}{9}+\dfrac{8}{12}+\dfrac{10}{15}+\dfrac{12}{18}+\dfrac{14}{21}\)
\(=\dfrac{4}{9}+\dfrac{2}{3}+\dfrac{2}{3}+\dfrac{2}{3}+\dfrac{2}{3}+\dfrac{2}{3}=\dfrac{4}{9}+\dfrac{10}{3}=\dfrac{4}{9}+\dfrac{30}{9}=\dfrac{34}{9}\)
\(=\dfrac{4}{9}+\dfrac{2}{3}+\dfrac{2}{3}+\dfrac{2}{3}+\dfrac{2}{3}+\dfrac{2}{3}=\dfrac{4}{9}+\dfrac{10}{3}=\dfrac{34}{9}\)