Question

derivada de f' (x)=x^-3

Answer 1

f(x)=x^-3

A derivada é..

f'(x) = -3x^-4

Answer 2

Derivada de potências:

$\boxed{\boxed{\dfrac{d}{dx}x^{n}=n\cdot x^{n-1}~~\forall~ n\in\mathbb{R}}}$
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$f'(x)=x^{-3}\\\\\\f''(x)=\dfrac{d}{dx}x^{-3}\\\\\\f''(x)=(-3)\cdot x^{-3-1}\\\\\\f''(x)=-3x^{-4}\\\\\\\boxed{\boxed{f''(x)=-\dfrac{3}{x^{4}}}}$