The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.3748+0.3261i\\[1 em]x_2 &= -0.3748-0.3261i\\[1 em]x_3 &= -0.1745+0.6684i\\[1 em]x_4 &= -0.1745-0.6684i\\[1 em]x_5 &= 0.6921+0.7295i\\[1 em]x_6 &= 0.6921-0.7295i \end{aligned} $$Polynomial $ 42x^6-12x^5+20x^4+8x^3+21x^2+12x+5 $ has no rational roots that can be found using Rational Root Test, so the roots were found using Newton method.