The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1442.5828\\[1 em]x_2 &= -720.7914+1249.0249i\\[1 em]x_3 &= -720.7914-1249.0249i \end{aligned} $$Polynomial $ -x^3+x^2-x+3000000000 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.