版上有许多询问97年的题目，就是没问到这题
是太简单了吗QQ
A number a is called a fixed pointed of a function f if f(a)=a.
Prove that if f'(x)≠1 for all real numbers x,
then f has at most one fixed point.
不常作这种证明题，恳请各位大哥大姊提点一下