The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.4591\\[1 em]x_2 &= -3.7296+1.8748i\\[1 em]x_3 &= -3.7296-1.8748i \end{aligned} $$Step 1:
Write polynomial in descending order
$$ \begin{aligned} -7x^2-x^3-14x+8 & = 0\\[1 em] -x^3-7x^2-14x+8 & = 0 \end{aligned} $$Step 2:
Polynomial $ -x^3-7x^2-14x+8 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.