Answer:
Step-by-step explanation:
Since 8 is a power of 2
[tex]\boxed{f(x)=k*2^{ax}}\\\\f(2)=k*2^{2a}\\f(-1)=k*2^{-a}\\\\\dfrac{f(2)}{f(-1)} =\dfrac{k*2^{2a}}{k*2^{-a}} =\dfrac{1}{8*8} \\\\2^{3a}=2^{-6}\\\\a=-2\\\\f(2)=k*2^{2a} \ \Longrightarrow\ k*2^{-4}=2^{-3}\\k=2\\\\\boxed{f(x)=2*2^{-2*x} =2^{-2x+1} }\\[/tex]
