Power series expansion

[dukebound85]

So I am trying to assist my younger brother with hw help and he's working on power series.......and despite having taken much math, I forgot how to do it lol

The function is this

g = g.o * (1+z/a)^-2 where g.o and a are constants and a>>z

I was playing around with my old text books and I was coming up with

g.0 + (1+z/a) * (z/a)^2 + (z/a)^3 ....etc but dont think its correct

 

[Hellhammer]

g.o * (1 + (a/z)^2)

g.o + g.o(a²/z²)

Can't promise that it's right but that's my guess.