导数如何解
2个回答
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lim(x->0) [f(x^3) -2x^2.f(x) ]/ln(1+x^3)
(等价无穷小)
=lim(x->0) [f(x^3) -2x^2.f(x) ]/x^3 (0/0)
(分子,分母分别求导)
=lim(x->0) [3x^2.f'(x^3) -2x^2.f'(x) -4xf(x) ]/(3x^2)
=lim(x->0) [3x.f'(x^3) -2x.f'(x) -4f(x) ]/(3x)
=lim(x->0) [3f'(x^3) -2f'(x)]/3 -lim(x->0) 4f(x) /(3x)
=[3f'(0) -2f'(0)]/3 - (4/3)f'(0)
=-f'(0)
(等价无穷小)
=lim(x->0) [f(x^3) -2x^2.f(x) ]/x^3 (0/0)
(分子,分母分别求导)
=lim(x->0) [3x^2.f'(x^3) -2x^2.f'(x) -4xf(x) ]/(3x^2)
=lim(x->0) [3x.f'(x^3) -2x.f'(x) -4f(x) ]/(3x)
=lim(x->0) [3f'(x^3) -2f'(x)]/3 -lim(x->0) 4f(x) /(3x)
=[3f'(0) -2f'(0)]/3 - (4/3)f'(0)
=-f'(0)
追问
倒数第二步没看懂
可以解释一下吗
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