For cma's question

來源: 於 2011-07-23 10:19:59 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

f=2/9(x-2)^2.  You can check that f(2)=0 and f(f(5))=0. So f(0)=8/9.