Question

Tìm n 
\(8^n\div2^n=16^{2011}\)

Answer 1

a) Ta có: \(8^n:2^n=16^{2011}\)

\(\Leftrightarrow4^n=\left(4^2\right)^{2011}\)

\(\Leftrightarrow n=4022\)

b) Ta có: \(2^n+2^{n+3}=144\)

\(\Leftrightarrow2^n\left(1+2^3\right)=144\)

\(\Leftrightarrow2^n=16\)

hay n=4

Answer 2

\(8^n\div2^n=16^{2011}\)

\(\left(8\div2\right)^n=\left(4^2\right)^{2011}\)

\(4^n=4^{4022}\)

\(\Rightarrow n=4022\)

mình nghĩ ý b là

\(2^n+2^{n+3}=144\)

\(2^n+2^n\cdot2^3=144\)

\(2^n\left(1+8\right)=144\)

\(2^n\cdot9=144\)

\(2^n=16\)

\(2^n=2^4\)

\(\Rightarrow n=4\)