Blog function test
this is A test
this is joy 
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| this | is |
|---|---|
| a | Table |
| Paragraph | Textaaaaaa |
[x+y=10]
$x^2 + 2x + 5 + \sqrt x = 0$
[\begin{cases}
x+y+z=10
x+2y+3z=20
x+4y+5z=30
\end{cases}]
$\sum_{i=1}^{n}$，$\sum_{i=1}^nx_i$,$\prod\limits_{i=1}^n$,$\frac 1 5$，$\frac{x+1}{x^2}$,$9 \times 8 = 72$ $5 \cdot 6 = 30$ $30 \div 6 = 5$
$y= \begin{cases} x^2, & x>0,\ x^2 +x-8, & x \le 0 \end{cases}$
[\begin{matrix}
1 & 2 & 3
4 & 5 & 6
7 & 8 & 9
\end{matrix}]
$e^{i\pi} + 1 = 0$
$E = mc^2$
$F=G \frac {m_{1}m_{2}}{R^{2}}$
$\begin{array}{lll}
\nabla\times E &=& -\;\frac{\partial{B}}{\partial{t}}
\ \nabla\times H &=& \frac{\partial{D}}{\partial{t}}+J
\ \nabla\cdot D &=& \rho
\ \nabla\cdot B &=& 0
\ \end{array}$
$\hbar\frac {\partial \psi} {\partial t} = \frac{-\hbar^2}{2m} \left(\frac{\partial^2} {\partial x^2} + \frac{\partial^2} {\partial y^2}+\frac{\partial^2} {\partial z^2} \right) \psi + V \psi$
The Cauchy-Schwarz Inequality
\(\left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)\)