Hi Guys

Since I last posted this question, I have figured out how to calculate part (i) and (ii). However, I am stuck on part (iii).

I think I need to use the formula (Inverse Function Rule), f '(z)=1/1-1/(f(z))^2). However, when I input the values of f(z) into the equation, i dont get the function as stated in part (iii). Am I missing something? Do i need to use parts (i) and (ii) of the answer? If so, for part (ii) I got z+4/z-16/z^3....

Please help someone - this is really doing my head in...!!