$$- \frac{2}{x^{2} + 1}$$
4*x
---------
2
/ 2\
\1 + x /
$$\frac{4 x}{\left(x^{2} + 1\right)^{2}}$$
/ 2 \
| 4*x |
4*|1 - ------|
| 2|
\ 1 + x /
--------------
2
/ 2\
\1 + x /
$$\frac{1}{\left(x^{2} + 1\right)^{2}} \left(- \frac{16 x^{2}}{x^{2} + 1} + 4\right)$$