define uniform convergence of this function: $fn(x)=n.x.(1-x)^n$

Question

$$f_{n}(x)=nx(1-x)^{n}$$ for $x \in I=[a,1]$, where $0<a<1$. I already found the limit of the function $f(x)=0$. How can I show that this function is uniformly convergent? Thank you for your help.