Do you mean additive inverse or multiplicitive inverse? I'm not sure right now, but wouldn't the multiplicitive inverse be the denominator (bottom number)over the numerator (top number)? If so, wouldnt the invrse of f(x) simply be f(x)=1/[f(x)] ( in the case of the last one, note that 1/[f(x)] would equal 4/(3x1))?I am not a mathemetician, nor do i like Algebra, but I think your question was a bit vauge. Sorry I couldn't help much.
