recall that to get the inverse of any expression, we start off by doing a quick switcharoo on the variables, and then solve for "y",
[tex]\bf \stackrel{f(x)}{y}=8\sqrt{x}\qquad \stackrel{inverse}{\boxed{x}=8\sqrt{\boxed{y}}}
\\\\\\
\cfrac{x}{8}=\sqrt{y}\implies \left( \cfrac{x}{8} \right)^2=y\implies \cfrac{x^2}{8^2}=y\implies \cfrac{x^2}{64}=y\implies \cfrac{1}{64}x^2=\stackrel{f^{-1}(x)}{y}[/tex]
