x - atan(3*x)
3 1 - -------- 2 1 + 9*x
54*x ----------- 2 / 2\ \1 + 9*x /
/ 2 \ | 36*x | 54*|1 - --------| | 2| \ 1 + 9*x / ----------------- 2 / 2\ \1 + 9*x /