Intuitively this is easy for me to understand, but I don't know how to start the proof. Can someone help me? 

> 
> Prove that any polynomial of the form $x^n+\sum\_{i<n}a\_{i}x\_{i}$, with $a\_{i}\in \mathbb{R}$ and $n$ *odd*, has at least one real root.
> 
> 
>