4.
[tex]\it x^2=(\sqrt2-5)^2 \Rightarrow x^2=(5-\sqrt2)^2 \Rightarrow \sqrt{x^2}=\sqrt{(5-\sqrt2)^2} \Rightarrow \\ \\ \Rightarrow |x|=5-\sqrt2 \Rightarrow x=\pm(5-\sqrt2) \Rightarrow \begin{cases}\it x_1=-5+\sqrt2\\ \\ \it x_2=5-\sqrt2\end{cases}[/tex]
