tính nhanh1+1/3+1/9+1/27+1/81+1/243+1/729

\(1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}+\frac{1}{729}\)

\(=\frac{1}{729}\left(729+243+81+27+9+3+1\right)\)

\(=\frac{1}{729}.1093=\frac{1093}{729}\)