Question

Chứng minh rằng :  \(\frac{1}{2}-\frac{1}{4}+\frac{1}{8}-\frac{1}{16}+\frac{1}{32}-\frac{1}{64}<\frac{1}{3}\)

 

Answer 1

\(\frac{1}{2}-\frac{1}{4}+\frac{1}{8}-...-\frac{1}{64}=\frac{1}{2}-\frac{1}{2^2}+\frac{1}{2^3}-..-\frac{1}{2^6}\) = A 

2A = 1 - 1/2 + 1/2^2 - ... - 1/2^5

2A + A = 1 - 1/2 + 1/2^2 - ... - 1/2^5 + 1/2 - 1/2^2 + 1/2^3 - 1/2^4 - .. - 1/2^6

     3A  = \(1-\frac{1}{2^6}=\frac{2^6-1}{2^6}\)

Answer 2

hơi đúng

Answer 3

Đặt A = 1/2 − 1/4 + 1/8 − 1/16 + 1/32 − 1/64 A = 1/2 − 1/4 + 1/8 − 1/16 + 1/32 − 1/64
2A = 1 − 1/2 + 1/4 − 1/8 + 1/16 − 1/322 A =1 − 1/2 + 1/4 − 1/8 + 1/16 − 1/32
3A = 2A + A = 1 − 1/64 < 1 ⇒ A < 1/3 .

Answer 4

chuẩn

Answer 5

Có câu trả lời rồi còn gì ạ

Answer 6

đổi sang rồi rút gọn đi là đc