Let $E/F$ be a finite extension and $F$ be a perfect field.
Here, perfect field means $char(F)=0$ or $char(F)=p$ and $F^p=F$.
How to prove $E$ is also perfect field?
For $char(F)=0$ case, it's trivial, but for $char(F)=p$, no improvement at all...
Give me some hints