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f-x-x-2n-Determinate-f-n-x-




Question Number 166813 by mathocean1 last updated on 28/Feb/22
f(x)=x^(2n)   Determinate f^((n)) (x)
$${f}\left({x}\right)={x}^{\mathrm{2}{n}} \\ $$$${Determinate}\:{f}^{\left({n}\right)} \left({x}\right) \\ $$
Answered by TheSupreme last updated on 28/Feb/22
f′(x)=αx^(α−1)   f^((k)) (x)=((2n!)/((2n−k)!))x^(2n−k)
$${f}'\left({x}\right)=\alpha{x}^{\alpha−\mathrm{1}} \\ $$$${f}^{\left({k}\right)} \left({x}\right)=\frac{\mathrm{2}{n}!}{\left(\mathrm{2}{n}−{k}\right)!}{x}^{\mathrm{2}{n}−{k}} \\ $$
Answered by Mathspace last updated on 28/Feb/22
f^((1)) (x)=2nx^(2n−1)   f^((2)) (x)=2n(2n−1)x^(2n−2)   by recurrence f^((p)) (x)=2n(2n−1)...(2n−p+1)x^(2n−p)   p=n ⇒f^((n)) (x)=2n(2n−1)....(n+1)x^n   =((2n(2n−1)...(n+1)n!)/(n!))x^n   =(((2n)!)/(n!))x^n
$${f}^{\left(\mathrm{1}\right)} \left({x}\right)=\mathrm{2}{nx}^{\mathrm{2}{n}−\mathrm{1}} \\ $$$${f}^{\left(\mathrm{2}\right)} \left({x}\right)=\mathrm{2}{n}\left(\mathrm{2}{n}−\mathrm{1}\right){x}^{\mathrm{2}{n}−\mathrm{2}} \\ $$$${by}\:{recurrence}\:{f}^{\left({p}\right)} \left({x}\right)=\mathrm{2}{n}\left(\mathrm{2}{n}−\mathrm{1}\right)…\left(\mathrm{2}{n}−{p}+\mathrm{1}\right){x}^{\mathrm{2}{n}−{p}} \\ $$$${p}={n}\:\Rightarrow{f}^{\left({n}\right)} \left({x}\right)=\mathrm{2}{n}\left(\mathrm{2}{n}−\mathrm{1}\right)….\left({n}+\mathrm{1}\right){x}^{{n}} \\ $$$$=\frac{\mathrm{2}{n}\left(\mathrm{2}{n}−\mathrm{1}\right)…\left({n}+\mathrm{1}\right){n}!}{{n}!}{x}^{{n}} \\ $$$$=\frac{\left(\mathrm{2}{n}\right)!}{{n}!}{x}^{{n}} \\ $$$$ \\ $$

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