Can someone give me some help on this problem? Let $\displaystyle f_n(x)=\frac{4}{4+x^n}$ on $\displaystyle [0,\infty)$

I think $\displaystyle \{f_n(x)\}$ converges to $\displaystyle f(x)=0$.

Now I want to determine if this convergence is uniform or not. I tried to take the derivative to use the Weierstrass-M test, but I am stuck on finding the sup.

Also, does this sequence converge uniformly if we change the domain to $\displaystyle (1,\infty)$