jesse, with cubic functions, you can have either 1 real zero or 3. This is like some basic theorem of algebra or something.

for x<sup>n</sup>, you can have n, n-2, n-4 etc real zeros. (you can have 0 zeros for an even function but must have at least one real zero for an odd function, that is, n is even or n is odd).

since n=3 in this case, the function is odd and can have 3 or 1 real zeros.