Hi ​@Tímea Eisner, 

Slido does not have a direct integration with Beamer and we do not support LaTeX code. You can view our available integrations here.  

You could take a screenshot of the mathematical formulas and then insert them as a picture into the poll. However it is not possible to add them to the options. You can view further information here.

So the option would be for example to ask the question in written form and then add the picture with options A,B,C that includes the mathematical formulas and your options in the poll would be just called A,B,C. That way your participants could vote for the options. 

Hope this helps.