LyX ⇒ error missing $ inserted with numbered formula(Cntrl+Alt+N)

[aydi]

good morning,
it's the first time that i use LYX. i met some problem when i want to write a numbered formula(Cntrl+Alt+N)
formula:(f(x)=a+b/c+d*f(P1)+a2+b2/c2+d2*f(P2)).an error appeared missing $ inserted.but formula on line it works very well.

could some one tell me how can i do that.

thanks an advance.

[d60pmp]

Can't replicate your problem I'm afraid. Try putting it in an inline equation, right clicking, select "display eqn" and "number whole formula" and try again. If it still doesn't work view the source (View->View Source) and post it here.