$$1 - \frac{4}{x^{2} + 1}$$
8*x
---------
2
/ 2\
\1 + x /
$$\frac{8 x}{\left(x^{2} + 1\right)^{2}}$$
/ 2 \
| 4*x |
8*|1 - ------|
| 2|
\ 1 + x /
--------------
2
/ 2\
\1 + x /
$$\frac{1}{\left(x^{2} + 1\right)^{2}} \left(- \frac{32 x^{2}}{x^{2} + 1} + 8\right)$$