Đáp án:
`text{Đặt A =}` `1 + 1/2 + 1/2^2 + 1/2^3 + ... + 1/2^{2012}`
`⇔ 2A = 1 + 2 + 1/2 + 1/2^2 + .... + 1/2^{2011}`
`⇔ 2A - A = (1 + 2 + 1/2 + 1/2^2 + .... + 1/2^{2011}) - (1 + 1/2 + 1/2^2 + 1/2^3 + ... + 1/2^{2012})`
`⇔ A = 2 - 1/2^{2012}`
`text{Vậy A=}` `2 - 1/2^{2012}`