The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.049\\[1 em]x_2 &= 10.4755+3.5052i\\[1 em]x_3 &= 10.4755-3.5052i \end{aligned} $$Polynomial $ -x^3+22x^2-144x+128 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.