The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3256\\[1 em]x_2 &= -0.8652\\[1 em]x_3 &= 1.3312 \end{aligned} $$Polynomial $ 24x^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.