$$F(x)=5x^{2}+15x-6ix=3$$
$x=\frac{\sqrt{249-180i}}{10}+\left(-\frac{3}{2}+\frac{3}{5}i\right)\approx -3.167704196+1.13966405i$
$x=-\frac{\sqrt{249-180i}}{10}+\left(-\frac{3}{2}+\frac{3}{5}i\right)\approx 0.167704196+0.06033595i$
