Câu trả lời:
\(2S=1+\frac{1}{2^2}+\frac{1}{2^3}+...........+\frac{1}{2^8}\)
\(2S-S=1+\frac{1}{2^2}-\frac{1}{2}-\frac{1}{2^9}\)
\(S=1+\frac{1}{4}-\frac{2}{4}-\frac{1}{2^9}\)
\(S=1-\frac{1}{4}-\frac{1}{2^9}\)
\(S=\frac{3}{4}-\frac{1}{2^9}\)
\(S=\frac{3.128-1}{2^9}=\frac{383}{512}\)