Let f (x) = x². Graph the functions f (x) + 1, f (x) - 1, f (x) + 2, and f (x) - 2. Make a guess about the relationship between the graph of a general function f (x) and the graph of f (x) + c for some constant c. Test your guess on the functions f (x) = x³ and f (x) = √x.