# Binomial Coefficients ${\frac{-1}{2} \choose n}$

i am trying to solve Exercises from Martin Aigner A Copurse in Enummarations, i am having problems with this one:

I got the first part(well you open the factorials by definition and put the 2's in the right positions, then close), but I am clueless where to start on the second one.

• – Robert Z Apr 17 '18 at 11:39
• awesome! :) this helps – thetha Apr 17 '18 at 11:39
• Hint: Try letting $r = -1/2$. – awkward Apr 17 '18 at 14:58