The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.3486\\[1 em]x_2 &= -0.9629\\[1 em]x_3 &= -0.5505+0.4259i\\[1 em]x_4 &= -0.5505-0.4259i\\[1 em]x_5 &= 0.4919+0.5863i\\[1 em]x_6 &= 0.4919-0.5863i \end{aligned} $$Polynomial $ 42x^6+60x^5+20x^4+8x^3+21x^2+18x+4 $ has no rational roots that can be found using Rational Root Test, so the roots were found using Newton method.