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
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
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two solutions:-32/9 and -128/9.
-jinjing-
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07/14/2011 postreply
10:42:34
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no sir!
-15少-
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07/14/2011 postreply
11:29:04
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yes,b=2,OK,b=8,fof has 5,5+(-)3SQUAT3/2,3roots.not good.
-jinjing-
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07/14/2011 postreply
16:43:38