# Math Help - Why is this not working?

1. ## Why is this not working?

$f(x) = a_3 x^3$
results in an invalid equation error.

2. ## Re: Why is this not working?

$f(x) = a_3 x^3$

I've had some problems with the TEXtags. I think on my computer the best way is to write the equation etc. and then mark the equation and press on the sigmabutton in advanced mode to wrap the equation with the TEXtags.

3. ## Re: Why is this not working?

Me too. Things that have worked earlier now producing a whole lot of invalid equations.