Two possible answers.

**a)** [`TexForm`](http://reference.wolfram.com/mathematica/ref/TeXForm.html) converts a Mathematica expression into something you can use to paste it in TeX:

 TeXForm[x/Sqrt[5]]
 ==> \frac{x}{\sqrt{5}}

A usually more convenient way of achieving this is right-clicking output, and selecting `Copy as | LaTeX`.

**b)** If all you're looking for is a neater display form *inside Mathematica*, then have a look at [`MatrixForm`](http://reference.wolfram.com/mathematica/ref/MatrixForm.html) and [`TraditionalForm`](http://reference.wolfram.com/mathematica/ref/TraditionalForm.html).

 m = {{1, 2}, {3, 4}};
 TraditionalForm[m]
 MatrixForm[m]
![enter image description here][1]

Be careful only to use these commands to *display already existing values*. For example, when you're writing something like

 m = TraditionalForm[{{1, 2}, {3, 4}}];
 Eigenvalues[m]

then `m` is not assigned the matrix, but its `TraditionalForm` representation, which does not behave like a matrix anymore. The output of the above is simply a silly line:

![enter image description here][2]


 [1]: https://i.sstatic.net/TeblV.png
 [2]: https://i.sstatic.net/YkSjB.png