Question

[Nguyễn Hải Nam]

A=1+2+\(2^2+2^3+.................+2^{2008}\)

B=\(2^{2009}\)

Answer 1

[Nguyễn Đình Dũng]

Ta có:

A = 1 + 2 + 2² + ... + 2²⁰⁰⁸

=> 2A = 2 + 2² + ... + 2²⁰⁰⁹

=> 2A - A = 2²⁰⁰⁹ - 1

=> A = 2²⁰⁰⁸ - 1 < 2²⁰⁰⁹ = B

Vậy B> A

Answer 2

[Lê Chí Công]

 2A=2+2^2+...+2^2009

2A-A=(2+2^2+...+2^2009)-(1+2+...+2^2008)

A=2^2009-1

=>A<B