Let be a quadratic equation.
It is given that, coefficient of x2 and the constant term of a quadratic equation have the same sign
⇒ ac > 0
⇒ 4ac > 0
⇒ −4ac < 0
⇒ 02 −4ac < 0
⇒ Discriminant < 0
⇒ Roots are imaginary
Hence, if the coefficient of x2 and the constant term of a quadratic equation have the same sign and if the coefficient of x term is zero, then the quadratic equation has imaginary roots.