$$- \frac{7}{49 x^{2} + 1}$$
686*x
------------
2
/ 2\
\1 + 49*x /
$$\frac{686 x}{\left(49 x^{2} + 1\right)^{2}}$$
/ 2 \
| 196*x |
686*|1 - ---------|
| 2|
\ 1 + 49*x /
-------------------
2
/ 2\
\1 + 49*x /
$$\frac{- \frac{134456 x^{2}}{49 x^{2} + 1} + 686}{\left(49 x^{2} + 1\right)^{2}}$$