a) \(81^x:3^x=27\)
\(\Rightarrow\left(3^4\right)^x:3^x=27\)
\(\Rightarrow3^{4x}:3^x=3^3\)
\(\Rightarrow3^{4x-x}=3^3\)
\(\Rightarrow3^{3x}=3^3\)
\(\Rightarrow3x=3\)
\(\Rightarrow x=\dfrac{3}{3}=1\)
b) \(\dfrac{125}{5^x}=5\)
\(\Rightarrow\dfrac{5^3}{5^x}=5\)
\(\Rightarrow5^{3-x}=5\)
\(\Rightarrow3-x=1\)
\(\Rightarrow x=3-1=2\)
c) \(\dfrac{64}{\left(-4\right)^x}=-256\)
\(\Rightarrow\left(-4\right)^x=-4^3:4^4\)
\(\Rightarrow\left(-4\right)^x=-4^7\)
\(\Rightarrow x=7\)
a: =>27^x=27
=>x=1
b: =>5^x=125/5=25
=>x=2
c: =>(-4)^x=-4^3:4^4=-4^7
=>x=7