Question

tính giá trị của biểu thức 

\(A=1-\frac{1}{3}+\frac{2}{15}+\frac{2}{35}+....+\frac{2}{195}+\frac{2}{255}\)

Answer 1

\(=1-\frac{1}{3}+\frac{2}{3.5}+...+\frac{2}{15.17}\)

\(=1-\frac{1}{3}+2.\left(\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{15.17}\right)\)

\(=1-\frac{1}{3}+2.\left(\frac{1}{3}-\frac{1}{17}\right)\)

\(=\frac{62}{51}\)

Answer 2

\(\Leftrightarrow A=1-\frac{1}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+....+\frac{2}{13.15}+\frac{2}{15.17}\)

\(\Leftrightarrow A=\frac{2}{1.3}+\frac{2}{3.5}+......+\frac{2}{13.15}+\frac{2}{15.17}\)

\(\Leftrightarrow A=1-\frac{1}{17}=\frac{16}{17}\)

Answer 3

à ừ nhầm tui sai rùi 

Answer 4

sai nặng

cố sửa nha bn

Answer 5

uk thanks