4Because, if  ∗     ∗     (2) ∗        ∗       ∗    ∗
x = f (x ) ⇒ f  (x ) = f(f(x )) = f(x ) = x etc, the point  ∗
x is also a solution of  ∗    (n)  ∗
x  = f  (x )  .