Question

[d b t]

Rút gọn biễu thức:A=1+1\2+1\2²+1\2³+.......1\2²⁰¹²

Answer 1

[Hoàng Tử Bóng Đêm]

ta có :

2.A=1/2+2/2²+...+1/2²⁰¹³

2.A-A=(2+1+1/2²+...+1/2²⁰¹¹)-(1+1/2+1/2²+...+1/2²⁰¹²)

=>A= 2-1/2²⁰¹²

Answer 2

[hungminecraft]

2A=2+1+1/2+1/2^2+...+1/2^2011

2A-A=A=(2+1+1/2+1/2^2+...+1/2^2011)-(1+1/2+1/2^2+...+1/2^2012)

A=2-1/2^2012