\( (x-\sqrt 2)^2-3(x-\sqrt 2)=0\\\leftrightarrow (x-\sqrt 2)(x-\sqrt 2-3)=0\\\leftrightarrow \left[\begin{array}{1}x-\sqrt 2=0\\x-\sqrt 2-3=0\end{array}\right.\\\leftrightarrow \left[\begin{array}{1}x=\sqrt 2\\x=\sqrt 2 +3\end{array}\right.\\Vậy\,\,S=\{\sqrt 2;\sqrt 2+3\}\)