$$- \frac{4}{16 x^{2} + 1}$$
128*x
------------
2
/ 2\
\1 + 16*x /
$$\frac{128 x}{\left(16 x^{2} + 1\right)^{2}}$$
/ 2 \
| 64*x |
128*|1 - ---------|
| 2|
\ 1 + 16*x /
-------------------
2
/ 2\
\1 + 16*x /
$$\frac{- \frac{8192 x^{2}}{16 x^{2} + 1} + 128}{\left(16 x^{2} + 1\right)^{2}}$$