$(x-√2)+3(x²-2)=0$
$⇔(x-√2)+3(x+√2)(x-√2)=0$
$⇔(x-√2)(3x+3√2+1)=0$
$⇔3(x-√2)(x+√2+\frac{1}{3})=0$
$⇔3(x-√2)(x+\frac{3√2+1}{3})=0$
$⇔\left[ \begin{array}{l}x-√2=0\\x+\frac{3√2+1}{3}=0\end{array} \right.⇔\left[ \begin{array}{l}x=√2\\x=-\frac{3√2+1}{3}\end{array} \right.$
Vậy $S=${$√2;-\frac{3√2+1}{3}$}.