求函数项级数收敛区间的一种新方法

对形如∑∞n=0anxkn+b(k∈,b∈)的幂级数,当其缺项的时候,不能直接用公式ρ=li mn→∞an+1an求其收敛半径与收敛区间(本文约定收敛区间不含端点),一般都是直接采用达朗贝尔(比值)判别法求其收敛半径与收敛区间.事实上,对这种幂级数只需先作一个变量代换,就可以采用公式法求解.本文给出了这种方法的理论证明,并将结论进行了推广,即利用变量代换与公式法同样可求形如∑∞anxkn+bs(k,s∈,b∈)形式的函数项级数的收敛区间.     

求幂级数收敛半径的方法

指出了文 [1 ]中一个考研题的错误解法 ,并给出求幂级数收敛半径的几种方法     

求幂级数收敛半径的方法

指出了[1]中一个考研题的错误解法，并给出求幂级数收敛半径的几种方法。     

用代数方法求幂级数的和函数

所谓用代数方法求幂级数的和函数是指仅用幂级数的加、减运算及已知的基本展开式来求幂级数在收敛区间内的和函数．有时,用这种方法比用逐项微分、逐项积分更简单、有效．先看一个简单的情形．命题一设数列是公差为d的等差数列,则对应幂级数的和函数为证由比值法容易求得这个幂级数的收敛半径两边同乘,得由于数列入是等差数列,即,故例1在收敛区间内,求幂级数的和函数．解。则幂级数变形为它的系数构成公差为的等差数列,,于是由（l）式得利用（l）式及命题一的证明方法,还能解决相邻两项系数之差构成等差数列的幂级数的求和问题．例…     

浅谈级数的应用与一点注记

该文通过对八个示例的分析及求解,介绍了级数在不等式证明、求高阶导数、计算一类定积分、解微分方程等四个方面问题中的应用.并简单介绍了综合利用数列极限理论和微分方程等工具研究幂级数的收敛域与和函数的方法和技巧.     

幂级数收敛半径的一些求法

讨论了在一些特殊情形下 ,幂级数收敛半径的求法     

无穷级数在求极限中的应用

求极限的方法虽然很多，但有一些极限题目求解仍然很困难，例如极限式是连乘积或和式形式，极限式含有n！或n的指数项等。在学习了无穷级数后；我们可以用无穷级数理论来求某些数列和函数的极限，这些方法为求极限问题提供了一种新的解题思路。本文用例题说明这些方法的应用。一、利用级数收敛的必要条件来极限一个数列Un的极限不易求出，如能将此看成某级数的通项，而对此级数收敛性的判定又较容易，则可由级数收敛的必要条件得出这个数列的极限为零。这种思路曾用于证明函数e“、sinx等幂级数展式中余项是趋于零的。对那些含有n！项、n的…     

数列与上、下极限

一、引言高等数学与初等数学的区别,除了研究对象不同外,主要是研究方法上的不同,而理解极限概念、掌握极限方法,是能否学好数学分析的关键,数列极限的学习又是学习极限理论的重要基础. 关于收敛数列的极限和性质等内容,在各类教材和有关材料中都有较详尽的讨论.这里,将对数列作进一步的讨论,介绍上,下极限的概     

用等价无穷小替换求极限的几点注释

在这篇文章里讨论了几个函数和与差的等价无穷小问题,对高等数学教材中利用等价无穷小替换求极限的适用范围进行了拓广,并得到了可用等价无穷小替换求极限的新的充要条件.     

有关幂级数在收敛区间端点上的性质的一些讨论

<正> 对于幂级数的分析运算,同济大学数学教研室主编的《高等数学》下册(1982年第二版)在叙述了幂级数经逐项求导或逐项积分后所得到的幂积数与原幂积数有相同的收敛半径R 以后,在250页有这样一段:     

Estimation of the measure of the image of the ball

Under study is the class of ring Q-homeomorphisms with respect to the p-module. We establish a criterion for a function to belong to the class and solve a problem that stems from M. A. Lavrentiev [1] on the estimation of the measure of the image of the ball under these mappings. We also address the asymptotic behavior of these mappings at a point.     

On the distributions of the ratios of the extreme roots to the trace of the Wishart matrix

In this paper, the authors cosider the derivation of the exact distributions of the ratios of the extreme roots to the trace of the Wishart matrix. Also, exact percentage points of these distributions are given and their applications are discussed.     

On the rational approximation of the sum of the reciprocals of the Fermat numbers

Let $\mathcal{G}(z):=\sum_{n\geqslant0} z^{2^{n}}(1-z^{2^{n}})^{-1}$ denote the generating function of the ruler function, and $\mathcal {F}(z):=\sum_{n\geqslant} z^{2^{n}}(1+z^{2^{n}})^{-1}$ ; note that the special value $\mathcal{F}(1/2)$ is the sum of the reciprocals of the Fermat numbers $F_{n}:=2^{2^{n}}+1$ . The functions $\mathcal{F}(z)$ and $\mathcal{G}(z)$ as well as their special values have been studied by Mahler, Golomb, Schwarz, and Duverney; it is known that the numbers $\mathcal {F}(\alpha)$ and $\mathcal{G}(\alpha)$ are transcendental for all algebraic numbers α which satisfy 0<α<1. For a sequence u, denote the Hankel matrix $H_{n}^{p}(\mathbf {u}):=(u({p+i+j-2}))_{1\leqslant i,j\leqslant n}$ . Let α be a real number. The irrationality exponent μ(α) is defined as the supremum of the set of real numbers μ such that the inequality |α?p/q|<q ^?μ has infinitely many solutions (p,q)∈?×?. In this paper, we first prove that the determinants of $H_{n}^{1}(\mathbf {g})$ and $H_{n}^{1}(\mathbf{f})$ are nonzero for every n?1. We then use this result to prove that for b?2 the irrationality exponents $\mu(\mathcal{F}(1/b))$ and $\mu(\mathcal{G}(1/b))$ are equal to 2; in particular, the irrationality exponent of the sum of the reciprocals of the Fermat numbers is 2.     

Refinement of the asymptotics of the power of the quantile test

One investigates the asymptotic properties of the quantile test, similar to the properties of the Pearson's chi-square test of fit.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 153, pp. 5–15, 1986.The author is grateful to D. M. Chibisov for useful remarks.     

On the approximation of positive operators and the behaviour of the spectra of the approximants

LetT be a positive linear operator on the Banach latticeE and let (S _n ) be a sequence of bounded linear operators onE which converge strongly toT. Our main results are concerned with the question under which additional assumptions onS _n andT the peripheral spectra (S _n ) ofS _n converge to the peripheral spectrum (T) ofT. We are able to treat even the more general case of discretely convergent sequences of operators.