Mathematics for IGCSE & O level - Equations (Section 7 - No. 17)
If the discriminant (b²-4ac) of a quadratic equation is negative, what does it tell you about the roots?
The roots are real and distinct.
The roots are real and equal.
The roots are complex (non-real).
There are no roots.
Paliwanag
A negative discriminant implies the square root of a negative number, hence complex roots.