Câu hỏi của Ánh Minh

Question

Chứng tỏ rằng 2+2^2+2^3+2^4+.........+2^19+2^20 chia hết cho 6

Nguyễn Lê Phước Thịnh · Accepted Answer

$2+2^2+2^3+2^4+...+2^{19}+2^{20}$

$=\left(2+2^2\right)+2^2\left(2+2^2\right)+...+2^{18}\left(2+2^2\right)$

$=6\left(1+2^2+...+2^{18}\right)⋮6$

Câu trả lời:

$2+2^2+2^3+2^4+...+2^{19}+2^{20}$

$=\left(2+2^2\right)+2^2\left(2+2^2\right)+...+2^{18}\left(2+2^2\right)$

$=6\left(1+2^2+...+2^{18}\right)⋮6$