test mathjax

Maths between dollars is inline: $\sum_{k=1}^n k = \frac{n(n+1)}{2}$.


$\sum_{k=1}^n k = \frac{n(n+1)}{2}$
$\sum_{k=1}^n k = \frac{n(n+1)}{2}$
Maths between slash-square-brackets is display: $$\sum_{k=1}^n k = \frac{n(n+1)}{2}$$
Maths between slash-square-brackets is display: $$\sum_{k=1}^n k = \frac{n(n+1)}{2}$$