Question

tính nhanh

a 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64

 

Answer 1

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{4}+...+\frac{1}{32}-\frac{1}{64}\)

\(=\frac{1}{1}-\frac{1}{64}=\frac{63}{64}\)

Answer 2

a) \(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{64}\)

\(2A=1+\frac{1}{2}+\frac{1}{4}+...+\frac{1}{32}\)

\(\Rightarrow2A-A=A=1-\frac{1}{64}=\frac{63}{64}\)