The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.0596\\[1 em]x_2 &= -0.5702\\[1 em]x_3 &= -0.2867+0.7859i\\[1 em]x_4 &= -0.2867-0.7859i\\[1 em]x_5 &= 0.673+0.7401i\\[1 em]x_6 &= 0.673-0.7401i \end{aligned} $$Polynomial $ 42x^6-6x^5+20x^4+8x^3+21x^2+18x+1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using Newton method.