\(\frac{2}{3}+\frac{2}{9}+\frac{2}{27}+\frac{2}{81}+\frac{2}{243}\)
\(=\left(\frac{2}{3}+\frac{2}{9}\right)+\frac{2}{27}+\frac{2}{81}+\frac{2}{243}\)
\(=\frac{8}{9}+\frac{2}{27}+\frac{2}{81}+\frac{2}{243}\)
\(=\left(\frac{8}{9}+\frac{2}{27}\right)+\frac{2}{81}+\frac{2}{243}\)
Tự làm tiếp nha