How to embed formulas in a line of text using OpenOffice Impress?

No, it is not possible to embed a formula or a graphical object in text in draw and impress.

In Libreoffice/Openoffice terms this would be called "anchoring the formula as a character". This is something that is possible in writer (contrary to one of the answers above).

TeXMaths is a great addition to Libreoffice, but can in no way help on this issue.

Unfortunately, this is a great deficiency that makes impress very very badly suited for any serious scientific presentation.

If you want to follow the state of this issue, look at https://www.libreoffice.org/bugzilla/show_bug.cgi?id=35033

If you want to support the addition of this feature to libreoffice, there is a bounty that you can contribute to at http://www.freedomsponsors.org/core/issue/473/allow-inline-graphics-formulas-in-impress-and-draw