The roots of polynomial $ p(t) $ are:
$$ \begin{aligned}t_1 &= 1.6768\\[1 em]t_2 &= -2.9316\\[1 em]t_3 &= 3.2548 \end{aligned} $$Polynomial $ 2t^3-4t^2-18t+32 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.