\[\frac{\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}}{a}\]

\(\begin{cases} \frac{c}{\left(a \cdot \frac{1}{2}\right) \cdot \frac{c}{b/2} - \left(b/2 - \left(-b/2\right)\right)} & \text{when } b/2 \le -2.496996520939034 \cdot 10^{+74} \\ \frac{\frac{a \cdot c}{\left(-b/2\right) + \sqrt{{b/2}^2 - a \cdot c}}}{a} & \text{when } b/2 \le -9.074512816801552 \cdot 10^{-91} \\ \frac{c}{\left(a \cdot \frac{1}{2}\right) \cdot \frac{c}{b/2} - \left(b/2 - \left(-b/2\right)\right)} & \text{when } b/2 \le -6.735949376426626 \cdot 10^{-136} \\ \frac{\left(-b/2\right) - \sqrt{{b/2}^2 - a \cdot c}}{a} & \text{when } b/2 \le 2.7032921376893094 \cdot 10^{+83} \\ \frac{\frac{1}{2}}{\frac{b/2}{c}} - \frac{b/2}{a} \cdot 2 & \text{otherwise} \end{cases}\)