Question: how to find the inverse of a function on a ti-84?
Answer: Enter your functions in the Y= editor. ... 
Press [2nd][MODE] to access the Home screen.
Press [2nd][PRGM][8] to insert the DrawInv function.
Press [ALPHA][TRACE] and choose the name of the function you entered. ... 
Press [ENTER] to display the graph of your function and draw the inverse of your function.