My older son was stuck on a question about inverse functions from his Precalculus book:
Assume that for all . Solve for .
We began by talking about what was giving him difficulty and then moved on to solving the problem.
Next we moved on to looking at the function on Mathematica. It was a little unlucky that the scale was different for the x- and y-axes, but I think the pictures still got the point across.
After we finished talking I posted about the problem on twitter and John Golden made a neat Desmos version of the problem: