Lebl-Basic-Analysis-I · Problem 4.1.8

The Derivative

Mathematics · derivative-chain-rule-power

Problem

Let f:I→Rf : I \to \mathbb{R} be differentiable. For n∈Zn \in \mathbb{Z}, let fnf^n be the function defined by fn(x):=(f(x))nf^n(x) := \bigl(f(x)\bigr)^n. If n<0n < 0, assume f(x)≠0f(x) \neq 0 for all x∈Ix \in I. Prove that (fn)′(x)=n(f(x))n−1f′(x)(f^n)'(x) = n\bigl(f(x)\bigr)^{n-1} f'(x).

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