Question

A=1+2+2^2+2^3+2^4+2^5+...+2^10.

Answer 1

A=1+2+2^2+2^3+...+2^10

=>2A=2+2^2+2^3+2^4+...+2^11

=>2A-A=(2+2^2+2^3+...+2^11)-(1+2+2^2+...+2^10)

=>A=2^11-1

=>A=2047

Vậy A=2047