When I write, for example, in Math.SE and I want some equation to appear in the middle of the line I just use
instead of just one dollar sign.
How can I do something similir in Lyx ? doing something like ctrl+M twice didn't work.
For an unnumbered equation, Ctrl + Shift + M, or Insert --> Math --> Display formula.
If you want a numbered equation, you can either
If you want several equations after one another, use one of the AMS environments, either