`2x^4-10x^3+11x^2+x-1=0`

$2x^4-10x^3+11x^2+x-1=0$
$⇔2x^2(x^2-3x-1)-4x^3+13x^2+x-1=0$
$⇔2x^2(x^2-3x-1)-4x(x^2-3x-1)+x^2-3x-1=0$
$⇔(2x^2-4x+1)(x^2-3x-1)=0$
$⇔$ \(\left[ \begin{array}{l}2x^2-4x+1=0\\x^2-3x-1=0\end{array} \right.\) 
$⇔$ \(\left[ \begin{array}{l}2(x-1)^2-1=0\\(x-\dfrac{3}{2})^2-\dfrac{13}{4}=0\end{array} \right.\) 
$⇔$ \(\left[ \begin{array}{l}(x-1)^2=\dfrac{1}{2}\\(x-\dfrac{3}{2})^2=\dfrac{13}{4}\end{array} \right.\) 
$⇔$ \(\left[ \begin{array}{l}x-1=±\dfrac{1}{\sqrt{2}}\\x-\dfrac{3}{2}=±\dfrac{\sqrt{13}}{2}\end{array} \right.\) 
$⇔$ \(\left[ \begin{array}{l}x=1±\dfrac{1}{\sqrt{2}}\\x=\dfrac{3}{2}±\dfrac{\sqrt{13}}{2}\end{array} \right.\) 
Vậy `S={1±1/\sqrt{2};3/2±13/\sqrt{2}}`