Question

[nguyenthimai]

tinh nhanh           A= 1/3+1/6+1/12+1/24+1/48+1/96

Answer 1

[Trắng_CV]

\(A=\frac{1}{3}+\frac{1}{6}+\frac{1}{12}+\frac{1}{24}+\frac{1}{48}+\frac{1}{96}\)

\(\Rightarrow3A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\)

\(\Rightarrow3A=1+1-\frac{1}{2}+\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+\frac{1}{8}-\frac{1}{16}+\frac{1}{16}-\frac{1}{32}\)

\(\Rightarrow3A=1+1-\frac{1}{32}\)

\(\Rightarrow3A=2-\frac{1}{32}\)

\(\Rightarrow A=\left(2-\frac{1}{32}\right):3=\frac{21}{32}\)

P/s : Đúng nha 

Answer 2

[Hạ Vy]

A= 1/3+1/3-1/6+1/6-1/12+1/12-1/24+1/24-1/48+1/48-1/96

A=1/3+1/3-1/96

A=2/3-1/96

A=63/32.