$\sum_{i=0}^n (-1)^k \cdot C(n,k)$ Use the Binomial Theorem to Show
$$\sum_{i=0}^n (-1)^k \cdot C(n,k)$$
I'm not sure where to start here . . . I know it is missing an $a^{n-k}$ and a $b^{k}$ term that maybe I should set to be 1?

Yes. What is $0=(1+(-1))^n$ according to the binomial theorem?
