The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.5098i\\[1 em]x_2 &= -0.5098i\\[1 em]x_3 &= -1.34+0.4071i\\[1 em]x_4 &= -1.34-0.4071i\\[1 em]x_5 &= 1.34+0.4071i\\[1 em]x_6 &= 1.34-0.4071i \end{aligned} $$Polynomial $ x^6-3x^4+3x^2+1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using Newton method.