$a, b, c \in \mathbb{R}$
For $D<0$, there is no real solution
Consider $D \geqslant 0$.
Case I: $D=0, \quad \alpha=\beta=-\frac{b}{2 a}$
i) if $b>0$, then $\quad \alpha, \beta<0$
ii) if $b<0$, then $\quad \alpha, \beta>0$
iii) if $b=0$, then $\alpha=\beta=0$