The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -3.1059\\[1 em]x_2 &= -4.4471+2.711i\\[1 em]x_3 &= -4.4471-2.711i \end{aligned} $$Polynomial $ 4x^3+48x^2+219x+337 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.