`|x^2 - 3x +3 | - |x^2 + 2x - 3| = 0`
`<=> |x^2- 3x+3| = |x^2+2x-3|`
`<=>`\(\left[ \begin{array}{l}x^2 - 3x +3 = x^2+2x - 3\\x^2 - 3x+3 = -x^2 - 2x +3\end{array} \right.\)
`<=> ` \(\left[ \begin{array}{l}-5x = -6\\ 2x^2 - x = 0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x = \dfrac{6}{5} \\ x(2x - 1) = 0\end{array} \right.\)
Dễ dàng tính ra `x \in {6/5 ; 0 ; 1/2}`
Vậy `S = {6/5 ; 0 ;1/2}`
