The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.1908\\[1 em]x_2 &= 1.3725\\[1 em]x_3 &= 3.8184 \end{aligned} $$Polynomial $ 4x^3-20x^2+17x+4 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.