When $$a \ne 0$$ , there are two solutions to $$ax^2 + bx + c = 0$$ and they are
$$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$
Discriminant: $$D = b^2-4ac$$
If $$\alpha$$ and $$\beta$$ are the roots of quadratic equation ($$ax^2 + bx + c = 0$$), then:
• $$\alpha + \beta = -{b \over a}$$
• $$\alpha \beta = {c \over a}$$
• $$(x - \alpha)(x - \beta) = 0$$