The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.4562\\[1 em]x_2 &= 0.7281+1.8948i\\[1 em]x_3 &= 0.7281-1.8948i \end{aligned} $$Polynomial $ x^3+2x+6 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.