Display the slide you want to add an equation to.
On the Insert menu, click Object.
Show Me
In the Object type list, click Microsoft Equation 3.0.
If Microsoft Equation 3.0 isn't available in the Object Type list, do the following:
On the View menu, point to Toolbars, and then click Customize.
Click the Commands tab, and then click Insert under Categories.
In the Commands box, click Equation Editor, and then drag it from the Commands box to a gray area on any toolbar.
Use the Equation Editor tools and menus to create the equation.
For Help on creating an equation, click Equation Editor Help Topics on the Equation Editor Help menu.
To return to PowerPoint, click Exit and Return to Presentation on the Equation Editor File menu.