Question

Cho A=2+2^2+2^3+2^4……+2^100 Chứng minh A chia hết cho 3

Answer 1

\(A=2\left(1+2\right)+2^3\left(1+2\right)+...+2^{99}\left(1+2\right)=3\left(2+2^3+...+2^{99}\right)⋮3\)