\(3x^4-10x^2+3=0\Leftrightarrow3x^4-9x^2-x^2+3=0\Leftrightarrow3x^2\left(x^2-3\right)-\left(x^2-3\right)=0\Leftrightarrow\left(x^2-3\right)\left(3x^2-1\right)=0\Leftrightarrow\)\(\left[{}\begin{matrix}x^2-3=0\\3x^2-1=0\end{matrix}\right.\)\(\Leftrightarrow\)\(\left[{}\begin{matrix}x^2=3\\x^2=\dfrac{1}{3}\end{matrix}\right.\)\(\Leftrightarrow\)\(\left[{}\begin{matrix}x=\pm\sqrt{3}\\x=\pm\dfrac{\sqrt{3}}{3}\end{matrix}\right.\)
Vậy S={\(\pm\dfrac{\sqrt{3}}{3};\pm\sqrt{3}\)}