Add equations that flows with the text in the keynote
One way of having equations flow with the text is to use the equation editor inside Keynote to create equations.

You can use Insert > Equation menu at the top of Keynote or press Alt ⌥+Command ⌘+E to activate the equation edtior.

The equation editor in Keynote supports both LaTeX and MathML. See this Apple Support page for more details.

Below is an example Keynote slide that includes an equation created with the equation editor: