$x$

$x^2$

$10^18$

$10^{18}$

$x_2$

$x_10$

$x_{10}$

$\sqrt{x}$

$\sqrt[n]{x}$

$\leq$

$\geq$

$\pm$

$\mp$

$\sigma(n)$

$\Sigma$

$\prod$

$\underset{x}{y}$

$\overset{x}{y}$

$\underset{i = 1}{\overset{n}{\Sigma}}$

$\vec{x}$

$\frac{x}{y}$

$( \frac{x}{y} )$

$\left( \frac{x}{y} \right)$

$\left \lfloor \frac{x}{y} \right \rfloor$

$\left \lceil \frac{x}{y} \right \rceil$

$|x| = \begin{cases}
x & x \geq 0\\
-x & x < 0
\end{cases}$

$1, 2, \ldots, n$

$\cdots, \ldots, \vdots$

$a \vdots b$

$S \subset T$

$S \subseteq T$

$x \times y$

$x \div y$

$x \mod y$

$x \equiv y \pmod {p}$

$x(w) = \begin{cases}
0, w = n\\
1, w = s
\end{cases}$

$\ x$

$\\ x$

$\underset{x = 1}{\overset{n}{\LARGE \Sigma}}\
\underset{y = x + 1}{\overset{n}{\LARGE \Sigma}}\ \sqrt{x + y}$

$\frac{1}{2}\ +\ \frac{1}{3}\ +\ \frac{1}{4}\ \ldots\ +\ \frac{1}{n}$

$F(x) = \begin{cases}
1&,\ x = 1\\
1&,\ x = 2\\
F(x - 1) + F(x - 2)&,\ x \geq 2\\
\supset
\end{cases}$

$\underset{i = 1}{\overset{n}{\Large \Sigma}} \left( \right)$