Slidify is highly modular, so that you only use components that you need. Extended functionality is achieved using widgets, which can be enabled in the YAML front-matter. So, to render latex equations, you need to enable the mathjax
widget
widget: [mathjax]
Now you can write equations
\[x = y + z\] \[f1 = \int_0^{\pi} exp(-x^2) dx\]