assuming is the inverse of the expression.
as you'd know, we first off do a quick switcharoo on the variables, and then solve for "y", so, let's do so,
[tex]\bf \stackrel{f(x)}{y}=x^2-16\qquad inverse\implies \boxed{x}=\boxed{y}^2-16
\\\\\\
x+16=y^2\implies \sqrt{x+16}=\stackrel{f^{-1}(x)}{y}[/tex]