$$- \frac{2 x}{x^{4} + 1}$$
/ 4 \
| 4*x |
2*|-1 + ------|
| 4|
\ 1 + x /
---------------
4
1 + x
$$\frac{\frac{8 x^{4}}{x^{4} + 1} - 2}{x^{4} + 1}$$
/ 4 \
3 | 8*x |
8*x *|5 - ------|
| 4|
\ 1 + x /
-----------------
2
/ 4\
\1 + x /
$$\frac{8 x^{3}}{\left(x^{4} + 1\right)^{2}} \left(- \frac{8 x^{4}}{x^{4} + 1} + 5\right)$$