只是微分MC一條... (急~)

2011-02-04 3:35 pm

L = L(x) , 如 x > 0, L'(x) = 1/x
如果 f(x) = L(x^-8), f '(x)=?

A. -8/x*L(x)^9
B. -8/x
C. 8L(x)^7/x
D. 8/x
E. 1/x
F. -1/x

如果唔准用積分, 點搵答案?

回答 (1)

2011-02-04 7:15 pm

✔ 最佳答案

f(x) = L(1/x^8)

Let y = 1/x^8

f'(x)

= L'(y)y'

= (x^8)(-8/x^9)

= -8/x

ANSWER: B

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