Don't know the steps in finding this derivative.
But the derivative is
The answer is:
n / 1\ / 1 / 1\\ |1 + -| *|- --------- + log|1 + -|| \ n/ | / 1\ \ n/| | n*|1 + -| | \ \ n/ /
n / 2 \ / 1\ |/ 1 / 1\\ 1 | |1 + -| *||- --------- + log|1 + -|| - -----------| \ n/ || / 1\ \ n/| 2| || n*|1 + -| | 3 / 1\ | |\ \ n/ / n *|1 + -| | \ \ n/ /
/ / 1 / 1\\\ | 3*|- --------- + log|1 + -||| | | / 1\ \ n/|| n | 3 | n*|1 + -| || / 1\ |/ 1 / 1\\ 2 3 \ \ n/ /| |1 + -| *||- --------- + log|1 + -|| - ----------- + ----------- - ----------------------------| \ n/ || / 1\ \ n/| 3 2 2 | || n*|1 + -| | 5 / 1\ 4 / 1\ 3 / 1\ | |\ \ n/ / n *|1 + -| n *|1 + -| n *|1 + -| | \ \ n/ \ n/ \ n/ /