a. 1/8=2ⁿ:16ⁿ

1/8=1/8ⁿ

=>n=1

b.27<3ⁿ<243

<=>3³<3ⁿ<3⁵

=>n=4

a) 1/8 . 16ⁿ = 2ⁿ

    1/8          = 2ⁿ : 16ⁿ

    1/8          = ( 2/16 )ⁿ

    1/8          = ( 1/8 )ⁿ

=> n = 1

b) 27 < 3ⁿ < 243

    3³ < 3ⁿ < 3⁵

=> n = 4

mk chắc chắn 100% là n >1

b)\(27< 3^n< 243\)

\(3^3< 3^n< 3^5\)

\(\Rightarrow3< n< 5\)

\(\Rightarrow n\in\left\{4\right\}\)

ok con de

Bài làm:

a) \(\frac{1}{8}.16^n=2^n\)

\(\Leftrightarrow2^{4n}=2^{n+3}\)

\(\Rightarrow4n=n+3\)

\(\Rightarrow3n=3\)

\(\Rightarrow n=1\)

Vậy n=1

b) \(27< 3^n< 243\)

\(\Leftrightarrow3^3< 3^n< 3^5\)

\(\Rightarrow3< n< 5\)

\(\Rightarrow n=4\)

Vậy n=4

Học tốt!!!!

a) \(\dfrac{1}{8}.16^n=2^n\)

=> \(2^{4.n-3}\)=\(2^n\)

=> \(4.n-3=n\)

=> \(n=1\)

b) \(27< 3^n< 243\)

=> \(3^3< 3^n< 3^5\)

=> \(n=4\)

\(\frac{2^{4n}}{2^3}=2^n\Leftrightarrow2^{4n-3}=2^n\Rightarrow4n-3=n\Rightarrow n=1\)

\(3^3< 3^n< 3^5\Rightarrow n=4\)

a)x ∈ ∅

b) x=3

\(a,\Rightarrow2^3< 2^x\le2^4\Rightarrow x=4\\ b,\Rightarrow3^3< 3^{12}:3^x< 3^5\\ \Rightarrow3^3< 3^{12-x}< 3^5\\ \Rightarrow12-x=4\Rightarrow x=8\)

a/ \(\frac{1}{8}.16^n=2^n\)

=> \(\frac{1}{8}.2^{4n}=2^n\)

=> \(\frac{2^n}{2^{4n}}=\frac{1}{8}\)

=> \(2^{n-4n}=2^{-3}\)

=> \(n-4n=-3\)

=> \(n=1\)

b/ 27 < 3ⁿ <243

hay 3³ < 3ⁿ < 3⁵

=> 3< n <5

=> n = 4