The question ask - in the real world, what might be a situation where it is preferable for the data to form a relation but not a function?
Also, if the variables in an equation were reversed, what would happen to the graph of the equation? This was the example I was given, how would the graph of y = x² relate to the graph of x = y²? When might such a reversal of variables be useful in the real world? I dont understand the questions, can this be explain in detail?