f(x)=(x+a)(x+b)
5^2 - 5 = 20
a = bq + r
L' = {L}{\sqrt{1-\frac{v^2}{c^2}}}
\begin{align} B'&=-\partial \times E,\\ E'&=\partial \times B - 4\pi j, \end{align}
A \overset{!}{=} B; A \stackrel{!}{=} B
\lim_{x\to 0}{\frac{e^x-1}{2x}} \overset{\left[\frac{0}{0}\right]}{\underset{\mathrm{H}}{=}} \lim_{x\to 0}{\frac{e^x}{2}}={\frac{1}{2}}
A \xleftarrow{\text{this way}} B \xrightarrow[\text{or that way}]{} C
\begin{align*} f(x) &= (x+a)(x+b) \\ &= x^2 + (a+b)x + ab \end{align*}
\begin{align} f(x) &= x^4 + 7x^3 + 2x^2 \nonumber \\ &\qquad {} + 10x + 12 \end{align}
\begin{align} f(x) &= \pi \left\{ x^4 + 7x^3 + 2x^2 \right.\nonumber\\ &\qquad \left. {} + 10x + 12 \right\} \end{align}
\begin{align} A &= \left(\int_t XXX \right.\nonumber\\ &\qquad \left.\vphantom{\int_t} YYY \dots \right) \end{align}
u(x) = \begin{cases} \exp{x} & \text{if } x \geq 0 \\ 1 & \text{if } x < 0 \end{cases}
a = \begin{dcases} \int x\, dx\\ b^2 \end{dcases}
\left.\begin{aligned} B'&=-\partial \times E,\\ E'&=\partial \times B - 4\pi j, \end{aligned} \right\} \qquad \text{Maxwell's equations}
\begin{alignat}{2} \sigma_1 &= x + y &\quad \sigma_2 &= \frac{x}{y} \\ \sigma_1' &= \frac{\partial x + y}{\partial x} & \sigma_2' &= \frac{\partial \frac{x}{y}}{\partial x} \end{alignat}
\boxed{x^2+y^2 = z^2}
\begin{align*} f(x) & = \int h(x)\, dx \\ & = g(x) \end{align*}
\lim_{a\to \infty} \tfrac{1}{a}
\lim\nolimits_{a\to \infty} \tfrac{1}{a}
\int_a^b x^2
\int\limits_a^b x^2
\sum\nolimits' C_n
\sum_{n=1}\nolimits' C_n
\sideset{}{'}\sum_{n=1}C_n
\sideset{_a^b}{_c^d}\sum
\prod_{\substack{ 1\le i \le n\\ 1\le j \le m}} M_{i,j}
x = a_0 + \frac{1}{a_1 + \frac{1}{a_2 + \frac{1}{a_3 + a_4}}}
x = a_0 + \frac{1}{\displaystyle a_1 + \frac{1}{\displaystyle a_2 + \frac{1}{\displaystyle a_3 + a_4}}}