In each case replace f(x) by y A) y = x B) y = x C) y = x Interchange the variables x and y A) x = y B) x = y C) x = y For each, ask the question "Is this equivalent to what it was before the variables were interchanged? A) Is x = y equivalent to y = x? Answer: NO B) Is x = y equivalent to y = x? Answer: NO C) Is x = y equivalent to y = x ? Answer: YES So the answer is C) f(x)=x Edwin