The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3244\\[1 em]x_2 &= -0.8757\\[1 em]x_3 &= 1.3774 \end{aligned} $$Polynomial $ 23x^3-19x^2-24x+9 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.