What does the parentheses mean in this problem?
$$\sum_{K=0}^4 {4\choose K} x^k y^{4-k}$$
4
Sigma Symbol (4)
(K) x^k y^4-k
K=0
The 4 and the k are in the same parentheses but the 4 is right above the k.It's on top, not side by side.