$f\left(x\right)=\frac{2x+9}{\sqrt{10x}}$

$f\left(x\right)=2x^{-1}+18$

$f\left(x\right)=\frac{1}{\sqrt{x}}$

$f\left(x\right)=\frac{7}{6x+2}$

$f\left(x\right)=\frac{x^{\frac{1}{2}}-6}{x+7}$