The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.0804\\[1 em]x_2 &= -0.8059\\[1 em]x_3 &= 0.8372\\[1 em]x_4 &= 2.0491 \end{aligned} $$Polynomial $ 9x^4-18x^3-7x^2+12x+1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.