(3 - 2x)2 + 4x2 - 9 = 0
<=> (2x - 3)2 + (2x - 3)(2x + 3) = 0
<=> (2x -3)(2x - 3 + 2x + 3) = 0
<=> 4x(2x - 3) = 0
<=> x(2x - 3) = 0
<=> \(\left[{}\begin{matrix}x=0\\2x-3=0\end{matrix}\right.\)
<=> \(\left[{}\begin{matrix}x=0\\x=\frac{3}{2}\end{matrix}\right.\)
Vậy S = {0; 3/2}