Maths — The Binomial Expansion

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

\binom{n}{k} = \frac{n!}{k!(n-k)!}

(1+x)^n \approx 1 + nx \quad (\text{small } x)

(a+b)^2 = a^2 + 2ab + b^2