The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.5473\\[1 em]x_2 &= 1.0933\\[1 em]x_3 &= 0.2737+0.474i\\[1 em]x_4 &= 0.2737-0.474i\\[1 em]x_5 &= -0.5467+0.9468i\\[1 em]x_6 &= -0.5467-0.9468i \end{aligned} $$Polynomial $ -14x^6+16x^3+3 $ has no rational roots that can be found using Rational Root Test, so the roots were found using Newton method.