The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.5251\\[1 em]x_2 &= -1.0952\\[1 em]x_3 &= 2.213\\[1 em]x_4 &= -3.1429 \end{aligned} $$Polynomial $ 2x^4+3x^3-14x^2-9x+8 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.