\(a,\frac{16}{2^n}=2\Rightarrow2^n=16:2\Rightarrow2^n=8\Rightarrow2^n=2^3\Rightarrow n=3\)

\(b,\frac{\left(-3\right)^n}{81}=-27\Rightarrow\left(-3\right)^n=81.\left(-27\right)\Rightarrow\left(-3\right)^n=-2187\Rightarrow3^n=3^7\Rightarrow n=7\)

\(c,8^n:2^n=4\Rightarrow4^n=4\Rightarrow n=1\)

\(a,\frac{16}{2^n}=2\)                                    \(b,\frac{\left(-3\right)^n}{81}=-27\)                                              \(c,8^n:2^n=4\)

\(\Rightarrow2^4=2^n.2\)                                 \(\Rightarrow\left(-3\right)^n=\left(-27\right).81\)                                \(\Rightarrow\left(8:2\right)^n=4\)

\(\Rightarrow4=n+1\)                                 \(\Rightarrow\left(-3\right)^n=\left(-3\right)^7\)                                        \(\Rightarrow4^n=4\)

\(\Rightarrow n=4-1=3\)                         \(\Rightarrow n=7\)                                                                \(\Rightarrow n=1\)

a) \(\frac{16}{2^n}=2\)

=> 16 = 2 . 2ⁿ 

=> 16 = 2ⁿ⁺¹

=> 2⁴ = 2ⁿ⁺¹

=> n + 1 = 4

=> n = 4 - 1

=> n = 3

Vậy n = 3

b) \(\frac{\left(-3\right)^n}{81}=-27\)

=> (-3)ⁿ = -27 . 81

=> (-3)ⁿ = (-3)³ . (-3)⁴

=> (-3)ⁿ = (-3)⁷

=> n = 7

Vậy n = 7

c) 8ⁿ : 2² =  bao nhiêu vậy ban?

Chuk bn hk tốt!

a)\(\frac{16}{2^n}=2\)

    \(\Rightarrow16:2=2^n\) 

         2ⁿ=8=2³

Vậy n=3

b)\(\frac{\left(-3\right)^n}{81}=-27\)

  \(\Rightarrow\)(-3)ⁿ=-27.81

      (-3)ⁿ=-2187=(-3)⁷

Vậy n=7

c)Mk ko hiểu bn ghi gì

a)\(\frac{16}{2^n}=2\)

\(\Rightarrow2^n=\frac{16}{2}=8=2^3\)

\(\Rightarrow n=3\)

b) \(\frac{\left(-3\right)^n}{81}=27\)

\(\Rightarrow\left(-3\right)^n=-27.81=-2187=\left(-3\right)^7\)

\(\Rightarrow n=7\)
c) thiếu đề

1.a.\(\left(1+\frac{2}{3}-\frac{1}{4}\right).\left(\frac{4}{5}-\frac{3}{4}\right)^2=\frac{17}{12}.\left(\frac{1}{20}\right)^2=\frac{17}{12}.\frac{1}{400}=\frac{17}{4800}\)

b. \(2\div\left(\frac{1}{2}-\frac{2}{3}\right)^3=2\div\left(-\frac{1}{6}\right)^3=2\div\left(-\frac{1}{216}\right)=2.\left(-216\right)=-432\)

2.a.\(\frac{16}{2^n}=2\Rightarrow2^n=16:2=8=2^3\Rightarrow n=3\)

b.\(\frac{\left(-3\right)^n}{81}=-27\Rightarrow\left(-3\right)^n=-27.81=-2187=\left(-3\right)^7\Rightarrow n=7\)

c. \(8^n:2^n=4\Rightarrow\left(8:2\right)^n=4\Rightarrow4^n=4^1\Rightarrow n=1\)

a, \(\frac{16}{2^n}=2\Leftrightarrow16=2^n.2\Rightarrow2^4=2^{n+1}\Rightarrow n+1=4\Rightarrow n=3\)

b) \(\frac{\left(-3\right)^n}{81}=-27\Rightarrow\left(-3\right)^n=-27.81\Rightarrow\left(-3\right)^n=-3^3.3^4\Rightarrow\left(-3\right)^n=\left(-3\right)^7\Rightarrow n=7\)

c, \(8^n:2^n=4\Leftrightarrow2^{3n}:2^n=2^2\Leftrightarrow2^{2n}=2^2\Leftrightarrow2n=2\Rightarrow n=1\)

\(\frac{16}{2^n}=1;2^n=8;n=3\)

\(\frac{\left(-3\right)^n}{81}=-27;\left(-3\right)^n=\left(-3\right)^7;n=7\)

\(8^n:2^n=4;\left(8:2\right)^n=4;4^n=4=4^1;n=1\)

\(a,\frac{16}{2^n}=2=>\frac{2^4}{2^n}=2=>2^4:2^n=2=>2^{4-n}=2=>4-n=1=>n=3\)

\(b,\frac{\left(-3\right)^n}{81}=-27=>\frac{\left(-3\right)^n}{3^4}=\left(-3\right)^3=>\frac{\left(-3\right)^n}{\left(-3\right)^4}=\left(-3\right)^3=>\left(-3\right)^{n-4}=\left(-3\right)^3=>n-4=3=>n=7\)

\(c,8^n:2^n=4=>\left(8:2\right)^n=4=>4^n=4=>n=1\)

a)

b)

c)

a) $\frac{16}{2^n}=\mathrm{2\; =>\; \backslash (\backslash dfrac\{2^4\}\{2^n\}=2\backslash Rightarrow2^\{4-n\}=2\backslash Rightarrow4-n=1\backslash Rightarrow\; n=3\backslash )}$

b,
\(\dfrac{\left(-3\right)^n}{81}=-27\Rightarrow\dfrac{\left(-3\right)^n}{\left(-3\right)^4}=-27\Rightarrow\left(-3\right)^{n-4}=\left(-3\right)^3\Rightarrow n-4=3\Rightarrow n=7\)

c,\(8^n:2^n=4\Rightarrow4^n=4\Rightarrow n=1\)

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

=> n - 4 = 3 => n = 7

c) 8n : 2n = 4

4n = 4.