Question

tính nhanh :

A = 1/2 + 1/4 + 1/8 + 1/16 + 1/32

Answer 1

\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\)

\(A=\frac{1}{2^1}+\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}+\frac{1}{2^5}\)

\(2A=1+\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}\)

\(2A-A=1-\frac{1}{2^5}\)

\(A=\frac{32}{32}-\frac{1}{32}\)

\(A=\frac{31}{32}\)