The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.0694\\[1 em]x_2 &= 0.33\\[1 em]x_3 &= 0.67\\[1 em]x_4 &= 0.9306 \end{aligned} $$Polynomial $ 70x^4-140x^3+90x^2-20x+1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.