Answer:
If it does not cross the x axis.
Step-by-step explanation:
If the quadratic equation does not cross the x axis (or more specifically, if the quadratic is an upward opening parabola and the vertex is above the x axis, or if the quadratic is a downward opening parabola and the vertex is below the x axis), it will have no real solution
The fundamental theorem of algebra says that quadratics must have 2 solutions, so the solutions must be imaginary.
