Discrete Structures

$$ x^21 \ne x^{21}

:\epsilon :\varepsilon


 * \zeta
 * \eta
 * \theta


 * \sigma
 * \varsigma
 * \tau
 * \upsilon
 * \phi
 * \varphi
 * \chi
 * \psi
 * \omega
 * \Gamma
 * \Delta
 * \Theta
 * \Lambda

$$

$$\frac{x^n-1}{x-1} = \sum_{k=0}^{n-1}x^k$$

$$

\frac {\overbrace{(m+n)}^mbox(m )\cdots} {\underbrace{(m-1)}}

\frac{(m+n)!}{m!n!}

$$