Do you know the Talor fomulla in Caculas?
I have been told that, for large z,
f(z) = [(z - 1) / (z + 1)]^(1/6)
= [(1-(1/z)) / (1 + (1/z))] by dividing through by z
= 1 - (1/3z) + (1/(18z^2)) + O(z^-3)
f(z) = 1 - (1/3z) + g(z) where g(z) = O(z^-2) as z --> infinity
I have no idea how why the 3rd and 4th lines are as they are. What is the working behind them?