Negative indices

Hi, I'm having problems trying to write a negative index. Whenever I do e.g y^2 it's fine, but y^-2 and the 2 goes back to a normal size number.

[tex]y^{-2}[/tex] gives

Of course you can put any number of symbols in there:

For subscripts, exponents, and the like that have more than one character (as in "-2", which is two characters), you need to employ the method that "-1" suggested above: put them in { }

Thanks guys.