How do math textbooks show this

here is an example:
http://i.imgur.com/kx9dl.png

easy, just go to word or any similar program, and it should have the equation option that allows you to input mathematical equations or fractions and such. maybe there are programs online too

Insert an equation using Equation

1.Click where you want to insert the equation.
2.On the Insert menu, click Object, and then click the Create New tab.
3.In the Object type box, click Microsoft Equation 3.0.
If Microsoft Equation Editor is not available, you may need to install it.

How?
If you originally installed Microsoft Office from a network file server or from a shared folder, you must install Equation Editor from that location. If you installed Office from a CD-ROM, you must install Equation Editor from the disc.
Quit all programs.Do one of the following: If you run Microsoft Windows 2000, double-click the Add/Remo