Question

5/2+5/6+5/18+5/54+5/162+5/486+5/1458

Giải ra cho mình nhé

Answer 1

3,748285322

Answer 2

374828532236

Answer 3

mình nhầm là 3,74828532236

Answer 4

\(=5\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{18}+...+\frac{1}{486}+\frac{1}{1458}\right)\)

\(=5\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.6}+...+\frac{1}{18.27}+\frac{1}{27.54}\right)\)

\(=5\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{6}+...+\frac{1}{18}-\frac{1}{27}+\frac{1}{27}-\frac{1}{54}\right)\)

\(=5\left(1-\frac{1}{54}\right)\)

\(=5.\frac{53}{54}\)

\(=\frac{265}{54}\)