-32/9

5为f(f(x))的独根 ==〉f(5) 为 f(x) 的极值点

==〉f(x) 的另一个根为 8

==> f(x) = a(x-2)*(x-8)

f(5) = -9a, f(f(5))=f(-9a)=a(-9a-2)*(-9a-8)=0

a=-2/9, (a=0 和a=-8/9 不符合f(f(x))独根的条件）

f(0)=-32/9

所有跟帖： 

• two solutions:-32/9 and -128/9. -jinjing- ♀ (0 bytes) () 07/14/2011 postreply 10:42:34

• no sir! -15少- ♂ (0 bytes) () 07/14/2011 postreply 11:29:04

• yes,b=2,OK,b=8,fof has 5,5+(-)3SQUAT3/2,3roots.not good. -jinjing- ♀ (34 bytes) () 07/14/2011 postreply 16:43:38