关于函数项级数一致收敛的专题讨论

$f命题:$设$f(x)$在[-1,1]上有连续的导函数,且$f(0)=0$

   $(1)$证明:$sumlimits_{n = 1}^infty  {frac{1}{n}fleft( {frac{x}{n}} ight)} $在[-1,1]上一致收敛

   $(2)$设$Sleft( x ight) = sumlimits_{n = 1}^infty  {frac{1}{n}fleft( {frac{x}{n}} ight)} $,证明:$Sleft( x ight)$在[-1,1]上连续可导

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$f命题:$$f(14武大七)$设函数项级数$sumlimits_{n = 1}^infty  {frac{{{n^{n + 2}}}}{{{{left( {1 + nx} ight)}^n}}}} $,则

   $(1)$级数在$left( {1, + infty } ight)$上收敛

   $(2)$级数在$left( {1, + infty } ight)$上非一致收敛,但在$left( {1, + infty } ight)$上连续

1

$f命题:$$f(04大连理工)$设${u_n}left( x ight)left( {n = 1,2, cdots } ight)$在$[a,b]$上可微,$sumlimits_{n = 1}^infty  {{u_n}left( x ight)} $在${x_0} in left[ {a,b} ight]$处收敛,$sumlimits_{n = 1}^infty  {{u_n}^prime left( x ight)} $在$[a,b]$上一致收敛,证明:$sumlimits_{n = 1}^infty  {{u_n}left( x ight)} $在$[a,b]$上一致收敛

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$f命题:$当$|x|<r$时,$sumlimits_{n = 0}^infty  {{a_n}{x^n}} $收敛于$f(x)$,证明:当${frac{{{a_n}}}{{n + 1}}{r^{n + 1}}}$收敛时,$int_0^r {fleft( x ight)dx}  = sumlimits_{n = 0}^infty  {frac{{{a_n}}}{{n + 1}}{r^{n + 1}}} $

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$f命题:$$f(09武大九)$设${u_n}left( x ight) = frac{1}{{{n^3}}}ln left( {1 + {n^3}x} ight),n = 1,2, cdots $,记$Sleft( x ight) = sumlimits_{n = 1}^infty  {{u_n}left( x ight)} $

(1)证明:$sumlimits_{n = 1}^infty  {{u_n}left( x ight)} $在$[0,b]$上一致收敛,而在$left( {0, + infty } ight)$上非一致收敛

(2)讨论$S(x)$的可微性

$f命题:$

附录

$f命题:$$(f{Bendixon判别法})$设$sumlimits_{n = 1}^infty {{u_n}left( x ight)} $为$left[ {a,b} ight]$上的可微函数项级数,且$sumlimits_{n = 1}^infty {{u_n}^prime left( x ight)} $的部分和函数列在$left[ {a,b} ight]$上一致有界

证明:如果$sumlimits_{n = 1}^infty {{u_n}left( x ight)} $在$left[ {a,b} ight]$上收敛,则必在$left[ {a,b} ight]$上一致收敛

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$f命题:$$(f{Dini定理})$设函数项级数$sumlimits_{n = 0}^infty {{u_n}left( x ight)} $的每一项及其和函数均在$left[ {a,b} ight]$上连续,且对每个$x in left[ {a,b} ight]$,

有$sumlimits_{n = 0}^infty {{u_n}left( x ight)} $是正项级数或负项级数,则$sumlimits_{n = 0}^infty {{u_n}left( x ight)} $在$x in left[ {a,b} ight]$上一致收敛

参考答案

原文地址:https://www.cnblogs.com/ly142857/p/3672882.html