Given that $P(x)=(x+1)^{2n}-x^{2n} -2x-1$ $(n>2)$.How can I show that there is a polynomial $Q(x)$ such that $P(x)=x(x+1)(2x+1)Q(x)$?

I really don't know how and from what I have to start with :/ In this exercise ... do we need to find $Q(x)$ ? 

Can someone help me ? Thanks