Lipschitz Continuous Polynomials Let f : R → R be a polynomial of degree d ≥ 2. Show that f is not Lipschitz continuous. Where exactly should I begin with this problem?

Let $P(x)=a_n x^n+\cdots+a_0$ a polynomial with $n\geq 2$. You should show that there's no $k$ such that
$$|P(x)-P(y)|\leq k|x-y|\quad\forall x,y\in\mathbb R.$$
