Câu hỏi của Hanagaki Takehitou

Question

D=1 + 2^1 + 2^2 + 2^3 +....+2^49 + 2^50

Vũ Cao Minh · Accepted Answer

$D=1+2^1+2^2+2^3+...+2^{49}+2^{50}$

$\Rightarrow2D=2^1+2^2+2^3+...+2^{50}+2^{51}$

$2D-D=\left(2^1+2^2+...+2^{50}+2^{51}\right)-\left(1+2+...+2^{49}+2^{50}\right)$

$2D-D=D=2^{51}-1$

Câu trả lời:

$D=1+2^1+2^2+2^3+...+2^{49}+2^{50}$

$\Rightarrow2D=2^1+2^2+2^3+...+2^{50}+2^{51}$

$2D-D=\left(2^1+2^2+...+2^{50}+2^{51}\right)-\left(1+2+...+2^{49}+2^{50}\right)$

$2D-D=D=2^{51}-1$