If we let $f_n(x)=\frac{x^2+nx}{n}$ for $x\in R$. I am trying to show that we can make $f_n$ converge uniformly on the interval $[R,-R]$ For any fixed $R\in(0,\infty)$
One way to show uniform convergence is using the M-test.
So I need to find a series M such that $\sum f_n<=M$ and then if the series $\sum M$ converges then $\sum f_n$ must converge.
But how can I find that series $\sum M$ and then apply the M test.