The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.0523\\[1 em]x_2 &= -0.6496\\[1 em]x_3 &= -0.3729+0.8084i\\[1 em]x_4 &= -0.3729-0.8084i\\[1 em]x_5 &= 0.6002+0.7239i\\[1 em]x_6 &= 0.6002-0.7239i \end{aligned} $$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.