The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 3.2382\\[1 em]x_2 &= -0.0477+0.5537i\\[1 em]x_3 &= -0.0477-0.5537i \end{aligned} $$Polynomial $ 7x^3-22x^2-7 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.