Compuhigh.com have asked that we remove this topic "in order to ameliorate the harm to later students who may find the question and answer in an internet search".
I have responded to them "I am awaiting permission from two forum members ... seems a shame as the student was very engaged in the process and learned a lot with members help, as would others visiting the page. There are likely to be many places on the internet (facebook, reddit, etc) where your students will find answers to previous questions, it seems easier to simply change your questions (even a little) every year."
Ignoring many arguments (and a heavy heart), it simply seems like a nice gesture to Compuhigh to remove it.
With your permission anonimnystefy and bob?
I found Wolfram uses f-¹(x): http://mathworld.wolfram.com/InverseFunction.html
It would be nice to simplify the page to f-¹(x) ... but in the intro I say "So the inverse of: 2x+3 is: (y-3)/2" and that does not sit well with using f-¹(x)
Nor with the table of inverses as ganesh mentions.