The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0\\[1 em]x_2 &= 1 \end{aligned} $$Step 1:
Factor out $ \color{blue}{ -x^4 }$ from $ -x^5+x^4 $ and solve two separate equations:
$$ \begin{aligned} -x^5+x^4 & = 0\\[1 em] \color{blue}{ -x^4 }\cdot ( x-1 ) & = 0 \\[1 em] \color{blue}{ -x^4 = 0} ~~ \text{or} ~~ x-1 & = 0 \end{aligned} $$One solution is $ \color{blue}{ x = 0 } $. Use second equation to find the remaining roots.
Step 2:
To find the last zero, solve equation $ x-1 = 0 $
$$ \begin{aligned} x-1 & = 0 \\[1 em] x & = 1 \end{aligned} $$