Then what you need are:
- pdflatex: To have it, you have to install texlive-latex-base package (I am not sure about this).
- textext: You can download suitable version at http://pav.iki.fi/software/textext/index.html
To install the textext package, just copy the textext.py and textext.inx files to the folder:
Finally, restart your Inkscape and try it. Note the LaTeX formula might appear in some place beyond your working window, so make sure to zoom out your working area and look around for your formula.