a, \(\frac{16}{2^n}=2\Leftrightarrow2\cdot2^n=16\Leftrightarrow2^{n+1}=2^4\Leftrightarrow n+1=4\Rightarrow n=3\)
b,\(\frac{\left(-3\right)^n}{81}=-27\Leftrightarrow\left(-3\right)^n=-3^3.3^4\Leftrightarrow\left(-3\right)^n=\left(-3\right)^7\Rightarrow n=7\)
c,\(8^n:2^n=4\Leftrightarrow\left(2^3\right)^n:2^n=2^2\Leftrightarrow2^{3n}:2^{2n}=2^2\Leftrightarrow2^{3n-2n}=2^2\Leftrightarrow2^n=2^2\Leftrightarrow n=2\)
câu 1. \(\frac{16}{2^n}\)=2 =>2n=16x2=32
2n=25 => n=5
câu 2.\(\frac{\left(-3\right)^n}{81}\)=-27=33 =>(-3)n =81x33
=(-3)4x(-3)3
=(-3)7
câu 3. 8n:4n=4=>(8:4)n=4
2n=4 =22
=>n=2
