Die positiven Lösungen der Gleichungy a −[y a ]=y b −[y b ]=y c −[y c ]

Ohne Zusammenfassung     

Third-order ordinary differential equations y′′′ = f(x,y, y′, y″) with maximal symmetry group

We present here, in compact form, the necessary and sufficient conditions for linearization of third-order ordinary differential equations y'''=f (x,y,y', y'') with maximal symmetry group via point transformation. A simple procedure to construct the point transformation using the isomorphism of the symmetry subalgebra sl(2, ?) is also presented. This subalgebra is the semi-simple part of the Levi-Decomposition for the 7-dimensional symmetry algebra.     

y=a~x与y=log_ax的交点问题

引理1　如果单调增函数与其反函数的图象有交点,那么交点一定在直线y =x上.证　设(a ,b)是函数y =f(x)与其反函数y=f- 1 (x)的图象的交点,则　　　　　b=f(a) ,b=f- 1 (a) ,( 1 )( 2 )由( 1 )得a =f- 1 (b) ( 3)因为f(x)与f- 1 (x)均为单调函数,且f(x)与f- 1 (x)具有相同的增减性.因为f(x)为定义域上的增函数,则f- 1 (x)也为定义域上的增函数.若a≠b ,当a >b时,由( 2 ) ,( 3)有f- 1 (b) >f- 1 (a) .所以b>a ,这与a >b矛盾.同理,当a 相似文献   

On the complete solution of ∈y″=y 3

In Ref. 1, the author claimed that the problem y=y ³ is soluble only for a certain range of the parameter . An analytic approach, as adopted in the following contribution, reveals that a unique solution exists for any positive value of . The solution is given in closed form by means of Jacobian elliptic functions, which can be numerically computed very efficiently. In the limit 0+, the solutions exhibit boundary-layer behavior at both endpoints. An easily interpretable approximate solution for small is obtained using a three-variable approach.     

关于方程(a(t,y)y′)′=f(t,y,y′)的某些边值问题的可解性

本文在假设α(t,y)为正连续函数的情形下,把Granas, Petryshyn, Schuur等关于方程y″=f(t, y, y′)在有限或无限区间上的边值问题的可解性推广到方程(α(t, y)y′)′=f(t, y, y′)所用方法是Leray-Schauder原理及Wazewski拓朴方法。     

探究x0x＋y0y=r^2与x0x＋y0y=x0^2＋y0^2耐的几何意义

问题背景苏教版教材必修二P105这样一道习题：已知圆C的方程是x^2＋y^2=r^2,求经过圆C上一点M（x0,y0）的切线的方程．     

函数y=a^x与y=logax图象交点个数探究

本刊 2 0 0 3年第 12期刊出了《关于函数 y =ax与 y =logax图象交点个数的研究》一文 ,文中作者综合应用了实验观察、归纳猜想、分析转化等多种数学方法和“几何画板” ,Qbasic编程语言、导数等数学工具 ,对函数 y =ax 与 y =logax的图象交点个数作了深入的研究 .本人对作者的综合应用能力和探究能力深感惊叹和钦佩 ,读后受益很多 .但需指出的文中作者利用“不完全归纳法” ,对a取一系列的特值 (a取 0 .5 ,0 .75 ,1.4 ,… ) ,分别作出函数 y =ax 与 y =logax的图象 ,再通过观察比较从而得出结论 :“函数 y =ax 与 y =logax(a >0 ,a≠ 1)图…     

Four step methods for y″=f(x,y)

A systematic investigation is undertaken here on the possible practical consequences of the fact that the linear four step methods for y″=f(x, y) form a family with a certain structure. The mentioned property is found to be surprisingly rich in consequences, and three of them are of particular importance: (i) drastic reduction in the number of iterations at each step, (ii) increased flexibility with respect to the start of integration and to the modification of the step size during the integration process, (iii) possibility of direct and simple appraisal of the local truncation error.     

函数y=a~x和y=loga~x图象的交点

指数函数ｙ＝ａｘ和对数函数ｙ＝ｌｏｇａｘ互为反函数，它们的图象关于直线ｙ＝ｘ对称．探讨这两个图象交点的个数和位置，有助于加深对这两个函数性态的了解，并可以纠正一些流行的不正确的认识．《数学通报》１９９８年第１期载文〔１〕探讨了ａ＞１时两个图象交点的情...     

General linear methods for y′′?=?f?(y?(t))

In this paper we consider the family of General Linear Methods (GLMs) for the numerical solution of special second order Ordinary Differential Equations (ODEs) of the type y????=?f(y(t)), with the aim to provide a unifying approach for the analysis of the properties of consistency, zero-stability and convergence. This class of methods properly includes all the classical methods already considered in the literature (e.g. linear multistep methods, Runge?CKutta?CNystr?m methods, two-step hybrid methods and two-step Runge?CKutta?CNystr?m methods) as special cases. We deal with formulation of GLMs and present some general results regarding consistency, zero-stability and convergence. The approach we use is the natural extension of the GLMs theory developed for first order ODEs.     

关于方程 +φ(y)+Ψ(y)η(y)=0的极限环问题

本文研究了(1)的极限环问题,给出了判定其有无闭轨及极限环唯一的若干准则。推广和改进了[1]的结果。     

Über die Differentialgleichungu x y =f(x,y, u,u x,u y )

Ohne ZusammenfassungDiese Arbeit wurde teilweise unterstützt von der United States Air Force [Air Force Office of Scientific Research-Contract AF 49 (638)-228]. Sie besteht aus drei Teilen. Teil I ist im vorangehenden Heft dieser Zeitschrift erschienen, Teil III erscheint im folgenden Heft. Formeln und Sätze sind in jedem Teil für sich durchnumeriert. Bei Verweisen bedeutet z. B. (I. 17) die Formel (17) von Teil I, Satz I. 5 bedeutet Satz 5 von Teil I.     

关于非线性方程εy″=f(x,y,y′,ε)奇异摄动边值问题解的估计

在本文中,我们研究边值问题其中ε为小的正参数,在f_(y′)≤-k<0和其它适当的限制下,存在一个解y(x,ε)并满足其中y_0(x)为退化问题f(x,y,y′,0)=0,0相似文献   

EXPLICIT TWO-STEP HIGH-ACCURACY METHODS FOR y" = f(x,y)

In this paper, an almost P-stable two-step sixth-order Hybrid method with phase-lag of order infinity and a class explicit eighth-order Obreckoff methods with phase-lag of order 10-24 are developed for the numerical integration of the special second-order periodic initial-value problems. These methods have the advantage of higher algebraic order and considerably smaller phase-tag compared with some methods in [1-6]. Numerical examples indicate that these new methods are more accurate than methods developed by [1-6].     

函数y=x2与y=ax的图象交点个数探究

北师大版普通高中课程标准实验教科书数学必修1第3.6节"指数函数、幂函数、对数函数增长的比较",借助"列表法"与"图象法"得到了函数y=x2与y=2x的图象在第一象限内有两个交点,那么函数y=x2与yax(a＞0且a≠1)的图象在第一象限内是否一定有两个交点?如果不是,交点情况又如何?本文拟对此作一探究.     

y=Asinωx和y=Acosωx的几何性质

函数y=Asin(ωx φ) k或y= Acos(ωx φ) k的最值、周期、单调代数性质等是大家都比较熟悉的.本文介绍它们的几个几何性质,供同学们学习参考.性质如图1和图2,M,N,P是函数y =Asinωx或y=Acosωx(A>0,ω>0)的图象上的三个相邻的两个最高点和一个最低