As the title says,

I want to know how to write a matrix and system of linear equation in Latex?

If you are looking for Latex codes for matrices, system of equations, etc, then please go to the page Latex and MathJax in WordPress.

To get $\begin{bmatrix}

1 & 2\\

3& 4

\end{bmatrix}$, write

```
$\begin{bmatrix}
1 & 2\\
3& 4
\end{bmatrix}$.
```

For an augmented matrix, try

```
\[
\left[\begin{array}{rrr|r}
1 & 0 & 0 & 1 \\
0 & 1 & 0 & 0 \\
0 & 0 & 1 & 0 \\
\end{array} \right]
\]
```

You get

\[

\left[\begin{array}{rrr|r}

1 & 0 & 0 & 1 \\

0 & 1 & 0 & 0 \\

0 & 0 & 1 & 0 \\

\end{array} \right]
\]

By writing

```
\[
\left[\begin{array}{rrr|rrr}
1 & 0 & 0 & 1 &1 & 1 \\
0 & 1 & 0 & 0 & 1 & 1 \\
0 & 0 & 1 & 0 & 0 & 1 \\
\end{array} \right]
\]
```

You get

\[ \left[\begin{array}{rrr|rrr}

1 & 0 & 0 & 1 &1 & 1 \\

0 & 1 & 0 & 0 & 1 & 1 \\

0 & 0 & 1 & 0 & 0 & 1 \\

\end{array} \right]\]
Here is the Latex code for the system of equations.

```
\[
\left\{
\begin{array}{c}
a_1x+b_1y+c_1z=d_1 \\
a_2x+b_2y+c_2z=d_2 \\
a_3x+b_3y+c_3z=d_3
\end{array}
\right.
\]
```

The result is

\[

\left\{

\begin{array}{c}

a_1x+b_1y+c_1z=d_1 \\

a_2x+b_2y+c_2z=d_2 \\

a_3x+b_3y+c_3z=d_3

\end{array}

\right.

\]
More latex codes can be found at the page MathJax in WordPress, especially latex codes useful for MathJax blogs.