Question

[nguyen thi huyen trang]

S=\(\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+\frac{2}{9\cdot11}+..........+\frac{2}{93\cdot95}\)

nhanh nha minh dang can gap do

Answer 1

[Trịnh Thành Công]

\(S=\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+...+\frac{2}{93.95}\)

\(S=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{93}-\frac{1}{95}\)

\(S=\frac{1}{5}-\frac{1}{95}\)

\(S=\frac{18}{95}\)

Vậy \(S=\frac{18}{95}\)

Answer 2

[Cô nàng cá tính]

Giải 

\(S=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{93}-\frac{1}{95}\)

\(=\frac{1}{5}-\frac{1}{95}\)

\(=\frac{18}{95}\)

Vậy S=\(\frac{18}{95}\)