Question 17
If $k$ is a positive number and $f$ is a function such that, for every positive number $x,$ $$
\left[f(x^2+1)\right]^{\sqrt x}=k,
$$ then, for every positive number $y,$ $$
\left[f\left(\frac{9+y^2}{y^2}\right)\right]^{\sqrt{\frac{12}{y}}}
$$ is equal to
\left[f(x^2+1)\right]^{\sqrt x}=k,
$$ then, for every positive number $y,$ $$
\left[f\left(\frac{9+y^2}{y^2}\right)\right]^{\sqrt{\frac{12}{y}}}
$$ is equal to