Câu trả lời:
a) \(\Leftrightarrow x^2-x-2x+2=0\)
\(\Leftrightarrow x\left(x-1\right)-2\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x-2\right)=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}x-1=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\x=2\end{matrix}\right.\)
Vậy S={1,2}
b) \(\Leftrightarrow\)2x2 +2x+3x +3 = 0
\(\Leftrightarrow\) 2x(x+1)+3(x+1) = 0
\(\Leftrightarrow\)(x+1)(2x+3) = 0
\(\Leftrightarrow\)\(\left\{{}\begin{matrix}x+1=0\\2x+3=0\end{matrix}\right.\) \(\Leftrightarrow\)\(\left\{{}\begin{matrix}x=-1\\x=\frac{-3}{2}\end{matrix}\right.\)
Vậy S={-1; \(\frac{-3}{2}\)}