一元二次方程的根的判别式的应用

一元二次方程的根的判别式是初中代数的重要内容之一 ,它在中学数学中有着广泛的应用 ,成为近几年全国各地中考的热点问题 .为了帮助读者更好地掌握好这部分知识内容 ,现对它在初中数学中的应用进行归纳 ,以餮读者 .应用一 :判断一元二次方程 (或二元二次方程组 )的根的情况 ;或已知根的情况 ,求方程 (或组 )中的待定系数的取值范围 .一元二次方程ａｘ2 +ｂｘ +ｃ =0 (ａ≠ 0 )的根的判别式为△ =ｂ2 - 4ａｃ,它与这个方程的根有着十分密切的关系 :( 1)△ >0 方程有两个不等的实数根 ;( 2 )△ =0 方程有两个相等的实数根 .( 3)△ <0 方程…     

多项式的根的一个性质的判定

文献[1]在讨论多项式型的函数迭代方程的局部解析解的存在性时涉及到了多项式的根的一个性质.本文给出了判定该性质是否成立的一个简洁的条件,证明了多项式λ_nzⁿ+…+λ₂z²+λ₁z+λ₀有一个根α满足inf{｜λ_nα^nm+…+λ₂a^2m+λ₁α^m+λ₀｜：m=2,3,…｝>0当且仅当如下两个条件之中至少有一个成立：(i)该多项式有一个根β满足｜β｜>1;(ii)该多项式有一个根β满足｜β｜<1,且λ₀≠0.     

单圈图的最大特征值的上界的改进

Let G（V, E） be a unicyclic graph, Cm be a cycle of length m and Cm G, and ui ∈ V（Cm）. The G - E（Cm） are m trees, denoted by Ti, i = 1, 2,..., m. For i = 1, 2,..., m, let eui be the excentricity of ui in Ti and ec = max{eui ： i = 1, 2 , m}. Let κ = ec＋1. Forj = 1,2,...,k- 1, let δij = max{dv ： dist（v, ui） = j,v ∈ Ti}, δj = max{δij ： i = 1, 2,..., m}, δ0 = max{dui ： ui ∈ V（Cm）}. Then λ1（G）≤max{max 2≤j≤k-2 （√δj-1-1＋√δj-1）,2＋√δ0-2,√δ0-2＋√δ1-1}. If G ≌ Cn, then the equality holds, where λ1 （G） is the largest eigenvalue of the adjacency matrix of G.     

图的邻域复形的同调群的不变性

本文研究了图的邻域复形同调群的不变性质。设G是一个简单连通图,x是G的一个顶点,以G/x表示G中剔去点v及其关联边而得到的图,给出了G和G/x的邻域复形的同阶同调群同构的充要条件。     

纯正的群的正则带的构造

本文研究纯正的群的正则带.在给出这类半群的若干特征后,建立了纯正的群的正则带的构造定理.作为应用,同时给出了纯正的群的右拟正规带的构造定理.     

多维的一般的BBM-Burgers方程解的逐点估计

研究R~n中一般的BBM-Burgers方程解的渐进行为.运用Green函数法和Fourier分析方法得到了在非零常状态u~*附近小扰动解的逐点估计,作为一个推论,又得到了L~p(R~n)(1≤p∞)空间解的最佳的衰减估计.     

树的最大特征值的上界的一个注记

设T是一个树,V是T的顶点集．记dv是υ∈V的度,△是T的最大顶点度．设υ∈V且dw=1．记k=ew+1,这里ew是w的excentricity．设δj′= max{dυ:dist(υ,w)=j},j=1,2,…,k-2,我们证明和这里μ1(T)和λ1(T)分别是T的Laplacian矩阵和邻接矩阵的最大特征值．特别地,记δo′=2．     

逆周期的交换半群生成的簇的子簇

In this paper, all subvarieties of the varieties Ak （k ∈N） generated by aperiodic commutative semigroups are characterized. Based on this characterization, the structure of lattice of subvarieties of Ak is investigated.     

鞅的极大函数的Lp-范数的上界

设 2 ≤ p<∞ ,(fn)是一个鞅 ,利用P(｜fn｜>λ‖T(fn)‖∞)型的概率指数界 ,其中 ,T是作用在鞅上的拟线性算子 ,本文估计了鞅的极大函数的Lp_范数的上界。本文结果改进与推广了先前由HITCZENKO [7,8,9]与作者 [1 0 ]得到的结果     

关于分次环的群环的根的注记

本文研究了分次环的群环的Jacobson根,Brown-MCcoy根和强素根及其分次根．     

Estimates for the classical parametrix for the Laplacian

We consider the integral operators which were used classically to give a parametrix and remainder for the Laplacian on a Riemannian manifold. Their kernels are defined in terms of the distance function. These operators are shown to be bounded operators on the L₂ Hilbert spaces of differential forms, under the hypotheses that the manifold be complete and of finite volume, and that it satisfy curvature bounds. Furthermore, the remainder is shown to be compact.     

Boundary conditions for the volume potential for the polyharmonic equation

In a bounded connected domain, we obtain boundary conditions for the volume potential for the polyharmonic equation.     

Wavelet moment method for the Cauchy problem for the Helmholtz equation

The paper is concerned with the problem of reconstruction of acoustic or electromagnetic field from inexact data given on an open part of the boundary of a given domain. A regularization concept is presented for the moment problem that is equivalent to a Cauchy problem for the Helmholtz equation. A method of regularization by projection with application of the Meyer wavelet subspaces is introduced and analyzed. The derived formula, describing the projection level in terms of the error bound of the inexact Cauchy data, allows us to prove the convergence and stability of the method.     

Axioms for the equivariant Lefschetz number and for the Reidemeister trace

We characterize the Reidemeister trace, the equivariant Lefschetz number and the equivariant Reidemeister trace in terms of certain axioms. Dedicated to Albrecht Dold and Edward Fadell     

On Li's criterion for the Riemann hypothesis for the Selberg class

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In this paper, we shall prove a generalization of Li's positivity criterion for the Riemann hypothesis for the extended Selberg class with an Euler sum. We shall also obtain two arithmetic expressions for Li's constants , where the sum is taken over all non-trivial zeros of the function F and the indicates that the sum is taken in the sense of the limit as T→∞ of the sum over ρ with |Imρ|?T. The first expression of λF(n), for functions in the extended Selberg class, having an Euler sum is given terms of analogues of Stieltjes constants (up to some gamma factors). The second expression, for functions in the Selberg class, non-vanishing on the line , is given in terms of a certain limit of the sum over primes.

Video

For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=EwDtXrkuwxA.     

On the monodromy group for the contact problem for plane curves

Summary Fixr≥2,N=r(r+3)/2 andN smooth plane curvesA ₁…,A _N with degA _i>-2 fori=l,…,N. Then the monodromy group for the plane curves of degreer tangent tog _iA_i, g_i∈PGL(3), is the full symmetric group.

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Riassunto Sianor≥2,N=r(r+3)/2 eA ₁…,A _N curve piane lisce di grado almeno 2. Si dimostra che la monodromia per le curve piane di grador tangenti ag ₁ A _i,g _i∈PGL(3), è il gruppo simmetrico.

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Supported in part by NATO junior fellowship at M.I.T.