Question

Expand (1-a)^(-1/2) using the binomial theorem (and explain how the binomial theorem works with fractional (and negative) exponents!)

Answer 1

Here, http://en.wikipedia.org/wiki/Binomial_series ， I've learnt how to google.

Answer 2

1 + (-1/2) (-a)/1 + (-1/2)(-1/2-1)(-a)^2/2!+(-1/2)(-1/2-1)(-1/2-2)(-a)^3/3!+ ....
http://www4a.wolframalpha.com/Calculate/MSP/MSP5761a1chf6f063g9270000065gb6c967ac5929b?MSPStoreType=image/gif&s=18&w=264&h=49