The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.7414\\[1 em]x_2 &= 1.2657\\[1 em]x_3 &= 3.0132\\[1 em]x_4 &= 0.1267+0.5641i\\[1 em]x_5 &= 0.1267-0.5641i\\[1 em]x_6 &= -0.2287+0.6905i\\[1 em]x_7 &= -0.2287-0.6905i \end{aligned} $$Polynomial $ 6x^7-20x^6+4x^5+2x^4+7x^3+9x^2+x+3 $ has no rational roots that can be found using Rational Root Test, so the roots were found using Newton method.