Question

Số tự nhiên thỏa mãn là

Answer 1

11

Answer 2

Đặt \(A=2^0+2^1+2^2+...+2^{21}\)

\(\Rightarrow2A=2^1+2^2+2^3+...+2^{22}\)

\(\Rightarrow2A-A=2^{22}-0\)

\(\Rightarrow A=2^{22}-1\)

\(\Rightarrow A=2^{2n}-1\)

\(\Rightarrow2n=22\)

\(\Rightarrow n=\frac{22}{2}\)

\(\Rightarrow n=11\)

Vậy \(n=11\)