Inversing x "parts" in a sequence of functions when x>0 for simple convergence

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I am currently studying for an Analysis exam and I have come across this problem in a textbook:

Study the simple and uniform convergence of this sequence of functions in $(0,\infty)$. $$f_n(x)=\frac{nx}{1+n^2x^2}$$

I was going to first check the simple convergence by taking the limit of $f_n(x)$, which is $\lim_{n\to\infty} \frac{nx}{1+n^2x^2}$ when $x>0$, but in my textbook, it says that for $x>0$, $f_n(x)=\frac{\frac{1}{nx}}{1+\frac{1}{n^2x^2}}$.

Can anybody help me figure out why the parts with the $x$ variable are inverted?