When we graph a function of a real variable, we need two dimensions: one
for the domain and one for the range. For example if we graph the function
u = x over the domain -1 <x< 1, then the graph is the diagonal of a
square.
The graph of u = x2.
Similarly the graph of the function u =
x2 fits inside a square in the plane, as do the
graphs of all the other power functions u =
xn for positive integers n.
