Here is an inline math \sum_{i=1}^nx_iy_i and \displaystyle \sum_i^n a_i this is a display math \sum_{i=1}^nx_iy_i. You can hover your mouse over the math symbols to see the corresponding latex code.
\sum_{i=1}^n a^2+b^2
If you dont't like the border around the image, go to the dashboard---> layout ---> edit html and look at the following code
.post img {
border:1px solid #CCCCCC;
padding:4px;
}
and remove the second line (border:... etc) or replace 1px into 0px.
Here are more examples:
Matrix
\begin{pmatrix}a&b&c\\d&e&f\\g&h&i\end{pmatrix}
Multiline Equation
\begin{aligned}x^2+4x-21&=0\\x^2+4x&=25\\x^2+4x+4&=21+4\\(x+2)^2&=25\\x+2&=\pm 5\\x&=-2\pm 5\end{aligned}
Commutative Diagram
\usepackage[all]{xy}\xymatrix{0\ar[r]&A\ar[d]\ar[r]^f&B\ar[d]&\\&C\ar[r]_g&D\ar[r]&0}
With Color
\color{Magenta}\usepackage[all]{xy}\xymatrix{0\ar[r]&A\ar[d]\ar[r]^f&B\ar[d]&\\&C\ar[r]_g&D\ar[r]&0}
\color{Blue}A^2+z^5
\begin{tabular}\tiny{a}&\scriptsize{b}\end{tabular}
