The behaviour of the solution depends on the value of the discriminant, D = b2 – 4ac, (aptly named as it allows you to discriminate between solutions)
If D > 0: The equation has real roots (the parabola will intersect the x axis twice)
If D = 0: The equation has a repeated real root (the vertex of the parabola lies on the x axis)
If D < 0: The equation has no real roots but rather 2 complex roots (the parabola does not intersect the x axis)