作者betray911015 (回头太难)
看板trans_math
标题合成函数
时间Sun Sep 23 14:15:47 2007
suppose f is differetiable function and f(2)=3,f'(2)=2, f'(3)=4 ,
and (fof)'(2)=?
(fof) = f(f(x))
(fof)' = f'(f(x)) f'(x)
(fof)'(2) = f'(f(2))f'(2)
= f'(3) f'(2)
= 4 x 2
= 8
因为答案给12，不知我哪算错了
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