这是一个留言板

\( \displaystyle\frac a b \) \(\displaystyle\sum_{i=0}^N\int_{a}^{b}g(t,i)\text{d}t\) \(\displaystyle\begin{bmatrix}
{a_{11}}&{a_{12}}&{\cdots}&{a_{1n}}\
{a_{21}}&{a_{22}}&{\cdots}&{a_{2n}}\
{\vdots}&{\vdots}&{\ddots}&{\vdots}\
{a_{m1}}&{a_{m2}}&{\cdots}&{a_{mn}}\
\end{bmatrix}\)