The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3524\\[1 em]x_2 &= -0.5661\\[1 em]x_3 &= -5.2994\\[1 em]x_4 &= 8.5131 \end{aligned} $$Polynomial $ x^4-3x^3-46x^2-9x+9 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.