Question

tính tổng A=2+2^2+...+2^100

Answer 1

A=2+2^2+...+2^100

2A=2^2+2^3+...+2^101

2A-A=2^101+2^100+...+2^2-(2^100+...+2^2+2)=2^101-2

Answer 2

A=2+2^2+...+2^100

2A=2^2+2^3+...+2^101

2A-A=(2^2+2^3+...+2^101)-(2+2^2+...+2^100)

A=2^101-2