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