Test MathJax
<hr><!--kg-card-begin: markdown--><p>$$\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}$$</p>
<!--kg-card-end: markdown--><!--kg-card-begin: markdown--><div> 
    $$
    A=\begin{bmatrix}
    a & b\\
    c & d\\
    e & f
    \end{bmatrix}
    $$
</div><!--kg-card-end: markdown-->
$$\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}$$



$$
A=\begin{bmatrix}
a & b\\
c & d\\
e & f
\end{bmatrix}
$$

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