Provide the Missing Information $\text { For positive integers } n \text { and } k(k \leq n+1) \text {, the } k \text { th term of }(a+b)^{n} \text { is given by }$

Provide the missing information.
- $\text { For positive integers } n \text { and } k(k \leq n+1) \text {, the } k \text { th term of }(a+b)^{n} \text { is given by }$