c
$\Delta=\left|\begin{array}{ccc} 1 & 2 & 1 \\ 2 & 3 & -1 \\ -2 & 1 & 2 \end{array}\right|$
$=(6+ y )-2((2 \alpha-\alpha)+1(\alpha+3 \alpha)$
$=7-2 \alpha+4 \alpha$
$=7+2 \alpha$
$\Delta=0 \Rightarrow \alpha=-\frac{7}{2}$
$\Delta_{1}=\left|\begin{array}{ccc}2 & 2 & 1 \\ \alpha & 3 & -1 \\ -\alpha & 1 &2\end{array}\right|$
$=14+2 \alpha$
$\alpha=-x_{2}=7$
$\Delta_{1} \neq 0$