The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 11.8615\\[1 em]x_2 &= -8.1761\\[1 em]x_3 &= 26.3146 \end{aligned} $$Step 1:
Write polynomial in descending order
$$ \begin{aligned} 2552-30x^2+x^3 & = 0\\[1 em] x^3-30x^2+2552 & = 0 \end{aligned} $$Step 2:
Polynomial $ x^3-30x^2+2552 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.