So if you know about combining like terms(if not I reccomend watching a video online), then the different variables are x squared, xy, and z. These are all the variables. I hope this helps!
For function , the notation means that when the input to the function is , the output would be .
The inverse function of a one-to-one function is commonly denoted as .
The inverse function undoes the action of the original function. In this question, maps to . Thus, would need to map back to . Therefore, should be the corresponding input and output values.