关于Szeg(o)的一个不等式

设pn(x)为[0,∞)上次数不超过n的代数多项式,则有‖p′n(x)e-x‖[0,∞)≤(6.3n+1)‖pn(x)e-x‖[0,∞).若pn(x)同时又是奇函数或偶函数,则有‖p′n(x)e-x‖[0,∞)≤(1.8+7n1/2)‖pn(x)e-x‖[0,∞).     

一类不等式成立的条件与均值不等式的加强

熟知 ,不等式ax2 +bx +c≥ 0 (x≥ 0 )成立的充要条件是a≥ 0 ,c≥ 0 ,b+ 2ac≥ 0 .对此加以推广 ,我们得到了定理 1　设n∈R ,n >1 ,则不等式fn(x) =axn+bx +c≥ 0 .(x≥ 0 ) ( 1 )成立的充要条件是a≥ 0 ,c≥ 0 ,(n - 1 )b +n[(n - 1 )acn - 1 ]1 n≥ 0( 2 )证　先考虑a =1的情况 :易知b≥ 0时fn(x)在 [0 ,+∞ )上递增 ,b <0时 fn(x)在 [0 ,x0 ]与 [x0 ,+∞ ]上分别递减与递增 ,其中x0 =-bn1 n- 1 .故当x≥ 0时有fn(x) min=f( 0 ) =cf(x0 ) =c- (n - 1 )x0 n　 (b≥ 0 ) ,(b<0 ) .从而知 fn(x)≥ 0 (x≥ 0 )成立的充要条件是b≥ 0 ,c≥ 0…     

关于函数及其导数相互关系的几个结论

讨论由f(x)和f^(n 1)(x)的性质来决定f‘(x),f‘‘(x)……f(n)(x)的相应性质,得到几个结论璧如：设f（x)在区间(a, ∞)有直到(n 1)阶的导数,那么当limx→ ∞f(x)=0且limx→ ∞f^(n 1)(x)=0时,必有limx→ ∞f(x)=0……limx→ ∞f^(n)(x)=0     

指数型算子的逼近性质

设f∈C_([A,B]),称L_n(f,x)=integral from n=A to B(f(u)W(n,x,u)du)为指数型算子.其中W(n,x,u)满足下列条件:i) W(n,x,u)≥0,ii)integral from n=A to B(W(n,x,u)du)=1,iii)(/(x))W(n,x,n)=(n/((x)))W(n,x,u).(u-x)这里(x)是阶不高于2没有重零点的代数多项式,并且(x)>0,x∈(A,B);若A,B±∞,则(A)=(B)=0.     

一个代数不等式的指数推广

文 [1 ]中 ,程龙海先生证明了下面不等式 :若 0≤ x,y≤ 1 ,则x2 y2 ( 1 - x) 2 y2 x2 ( 1 - y) 2 ( 1 - x) 2 ( 1 - y) 2≤ 2 2 . ( 1 )本文将 ( 1 )式作如下推广定理　若 0≤ x,y≤ 1 ,n≥ 2 ,n∈ N,则n xn yn n ( 1 - x) n yn n xn ( 1 - y) n n ( 1 - x) n ( 1 - y) n≤ 2 n 2 . ( 2 )引理　若 u≥υ≥ 0 ,n≥ 2 ,n∈ N,则n un υn ≤ u ( n 2 - 1 )υ. ( 3)证明　因为 u≥υ≥ 0 ,所以[u ( n 2 - 1 )υ]n=un ∑ni=1Cinun- i( n 2 - 1 ) ivi≥ un ∑ni=1Cin( n 2 - 1 ) iυn=un [∑ni=0Cin(…     

用方差的一个推论解竞赛题

若一组数据的个数是 n,则它们的方差是S2 =1n[(x21 x22 … x2n) - nx2 ],其中 x =1n(x1 x2 … xn) ,这是众所周知的 ,由它易得推论　 n(x21 x22 … x2n)≥ (x1 x2 … xn) 2 .证明　∵　 S2 ≥ 0 ,故有　 (x21 x22 … x2n) -n(x1 x2 … xnn ) 2≥ 0 ,即     

用〔F,d_n〕平均逼近周期函数

设f(x)∈L_(2π)的Fourier级数为 f(x)～a_0/2+sum from n=1 to ∞ (a_ncosnx+b_nsinnx)sum from n=0 to ∞(A_n(f,x)) (1)以s_n(f,x)sum from i=0 to n(f,x)表示(1)第n部分和。称序列     

APPROXIMATION OF CONTINUOUS FUNCTIONS BY THE GENERALIZED BERNSTEIN-BEZIER POLYNOMIALS

§1. Introduction In [1], for any α>0, and a function φ defined on [0,1], Geng-Zhe Change defined the generalized Bernstein-Bezier polynomial ofφ as follows: B_(n, a)(φ, x) = sum from k=0 to n φ(k/n){f_(nk)~a(x)-f_(n,k+1)~a,(x)} (1.1)where f_(n, n+1) (x) =0 and f_(n, k)(x) = sum from j=k to n x~j(1-x)~(n-j) k=0,1,...,n. (1.2)are the Bezier base functions of degree n.Obviously, for any x ∈(0, 1), we have     

On the Schinzel Identity of Cyclotomic Polynomial

For integer n>0, let n(x) denote the nth cyclotomic polynomial n(x)=tackrel{01 be an odd square-free number.Aurifeuille and Le Lasseur［1］ proved thatequationn(x)=An2(x)-(-1)n-12)nxBn2(x).equation     

用求导法解2001年高考第20(Ⅱ)题

20 0 1年高考数学试卷理科第 2 0 ( )题为 :已知 r、m、n是正整数 ,且 1( 1 n) m .标答中是应用二项式定理来解 ,多数考生是用均值不等式法 (见本期 P4 2 ) .这里给出构造辅助函数和用求导的方法 .解∵　 11,∴　 f′( x) <0 ,则　 f( x)为单调递减函数 .又　 2≤ m ln( 1 n)n ,nln( 1 m) >mln( 1 n) .故…     

Nonoscillation theorems of second order nonlinear differential equations

The main purpose of this paper is to study the existence of nonoscillatory solutions of the second order non-linear differential equation (1). The author first generalizes a Wintner's lemma [1,8] to nonlinear equations (i.e. the following Theorem 1 and 4), and then obtains the necessary and sufficient conditions for the existence of nonoscillatory solutions of (1). These theorems generalize the corresponding results of [1] to include nonlinear equations. Using the above results, the author further obtains a series of criterion theorems for the existence of nonoscillatory solutions and comparison theorems for the oscillation and nonoscillation of nonlinear equations.     

Oscillatory and Asymptotic Behavior for Second Order Quasilinear Difference Equations

1 IntroductionConsider the second order quasilinear difference equationA(g(Ay.--l)) + f(n,y.) = 0, for n E N(no), (l'l)where A is defined by Ay. = Vn+1--yn, n E N(no) = {no, no + 1,'' }, nO E N = {l, 2,'. }.The following hold throughout the paPer:(H0) (i) g: R-R is a continuous increasing fUnction with propertiessgng(y) = sgny) g(R) = R;(il) f: N(no) x R--+ R is continuous as a function of y E R;(iii) yf(n,y) > 0 for n E N and y / 0.By a solution of the equation (1.l) we mean a non…     

Neutral delay differential equations with positive and negative coefficients

Consider the neutral delay differential equation [display math001] where [display math002] We studied the asymptotic behavior of the nonoscillatory solutions of Eq. (1) and we obtained sufficient conditions for the oscillation of all solutions, all bounded solutions, and all unbounded solutions of Eq. (1)     

二阶泛函微分方程的振动性质

在本文中，我们研究了一类较广泛的二阶非线性泛函微分方程的振动性质。文中指出，在一定条件下，方程的非振动解仅有两类，而且给出了每一类非振动解存在的必要条件，同时也建立了方程振动的若干充分判据。     

一阶中立型差分方程非振动解的分类

讨论了中立型差分方程的非振动解.首先由非振动解的渐进性质把非振动解分成两类.其次分别给出存在这两类非振动解的充分条件.最后给出例子说明定理的应用.     

Existence of nonoscillatory solutions of higher order neutral differential equations with distributed deviating arguments

In this work, we consider the existence of nonoscillatory solutions of variable coefficient higher order linear neutral differential equations with distributed deviating arguments. We use the Banach contraction principle to obtain new sufficient conditions, which are weaker than those known, for the existence of nonoscillatory solutions.     

高阶泛函微分方程的振动性质*

本文借助于Lebesgue测度等工具研究了一类高阶非线性泛函微分方程的振动性质.文中指出.在一定条件下,方程的非振动解仅有两类,而且给出了每一类非振动解存在的必要条件,同时也建立了方程振动的若干充分判据.     

The existence of nonoscillatory solutions of higher order nonlinear neutral equations

In this work, we consider the existence of nonoscillatory solutions of variable coefficient higher order nonlinear neutral differential equations. Our results include as special cases some well-known results for linear and nonlinear equations of first, second and higher order. We use the Banach contraction principle to obtain new sufficient conditions for the existence of nonoscillatory solutions.     

一类三阶拟线性微分方程非振动解的渐近性

主要讨论的是一类三阶拟线性微分方程(p(t)|u″|~(α-1)u″)′+q(t)|u|~(β-1)u=0其中α0,β0,p(t)和q(t)是定义在区间[a,∞)上的连续函数,且满足当t≥a时p(t)0,q(t)0.当t→∞时此方程满足∫_a~∞1/((p(t))~(1/α))dt=∞的特殊非振动解存在的充分必要条件.     

ASYMPTOTICS AND OSCILLATION FOR FIRST ORDER MIXED NEUTRAL DIFFERENTIAL EQUATIONS

1IntroductionConsidertheneutraldifferentialequationswherepiERfori=l,2,...,m;o相似文献