The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.6106\\[1 em]x_2 &= -2.4806\\[1 em]x_3 &= 0.435+1.2502i\\[1 em]x_4 &= 0.435-1.2502i \end{aligned} $$Polynomial $ x^4-3x^2+5x-7 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.