User:Eliasrg/Sandbox

=A Box of Sand=

Math
$$\pi = \sum_{n=0}^\infty \frac{4 (-1)^n}{2 n + 1}$$

$$e = \sum_{k=0}^\infty \frac{1}{k!}$$

$$e^{\pi i} + 1 = 0$$

Definitions
$$a b = \sum_{}^b a$$

$$a^b = \prod_{}^b a$$

$$ \begin{align} x^2 + p x + q & = 0\\ x^2 + p x + \left ( \frac{p}{2} \right )^2 & = \left ( \frac{p}{2} \right )^2 -q\\ \left (x + \frac{p}{2} \right )^2 & = \left ( \frac{p}{2} \right )^2 -q\\ x + \frac{p}{2} & = \pm \sqrt{\left ( \frac{p}{2} \right )^2 -q}\\ x & = -\frac{p}{2} \pm \sqrt{\left ( \frac{p}{2} \right )^2 -q}\\ \end{align} $$

$$f'(x) = \lim_{h \to 0} \frac{f(x+h) - f(x)}{h}$$