1. Zadatak

$$\begin{aligned} \sqrt x\left(\sqrt x-6\right)-2\left(\sqrt x-2\right)&=-11\\ x-6\sqrt x-2\sqrt x+4+11&=0\\ x-8\sqrt x+15&=0 \end{aligned}$$

Uvodimo supstituciju $\sqrt x=t$.

$$\begin{gathered} t^2-8t+15=0\\ t_1=3,\quad t_2=5\\ x_1=9,\quad x_2=25 \end{gathered}$$