Question

Tính

A=1/5+1/35+1/63+1/99+....+1/9999

Answer 1

\(\Rightarrow A=\frac{1}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{99}-\frac{1}{101}\right)+\frac{1}{5}\)

\(\Rightarrow A=\frac{1}{2}.\left(\frac{1}{5}-101\right)-\frac{1}{5}=\frac{48}{505}-\frac{1}{5}=-\frac{53}{505}\)

Answer 2

1/2 lấy đou ra z bn?