[tex]\it Vom\ \ nota:\\ \\ a=4\sqrt5,\ \ b=9[/tex]
[tex]\it \\ \\ \left. \begin{aligned} \it a^2=(4\sqrt5)^2=16\cdot5=80\\ \\ \it b^2=9^2=81\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \rule{0.1}{0.1}\end{aligned}\right\} \Rightarrow a^2 <b^2\Rightarrow a<b[/tex]
