The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 2.3909\\[1 em]x_2 &= -2.9434\\[1 em]x_3 &= 3.5525 \end{aligned} $$Polynomial $ x^3-3x^2-9x+25 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.