## n choose k

$${n \choose k} = _{n}^{k}\textrm{C}= \frac{n!}{k!(n-k)!}$$

https://byjus.com/n-choose-k-formula/

$$(x+y)^n = \sum_{k=0}^n %{n \choose k} x^{n - k} y^k$$

$$\label{eq:1} C = W\log_{2} (1+\mathrm{SNR})$$

## binomial theorem

In elementary algebra, the binomial theorem describes the algebraic expansion of powers of a binomial.

$$(a+b)^n=\sum_{k=0}^n{n\choose k}a^{n-k}b^k$$