考点4 函数的性质

1.(重庆卷,3)若函数f(x)是定义在R上的偶函数,在(-∞,0]上是减函数,且f(2)=0,则使得f(x)<0的x的取值范围是().(A)(-∞,2)(B)(2,+∞)(C)(-∞,-2)∪(2,+∞)(D)(-2,2)2.(山东卷,4)下列函数中既是奇函数,又在区间[-1,1]上单调递减的是().(A)f(x)=sinx(B)f(x)=-x+1(C)f(x)=12(ax+a-x)(D)f(x)=ln22-+xx3.(辽宁卷,10)已知y=f(x)是定义在R上的单调函数,实数x1≠x2,λ≠-1,α=x11++λλx2,β=x21++λλx1.若f(x1)-f(x2)相似文献   

特征为2的素环上强保持k-交换性的映射

令R是特征为2,且含有非平凡幂等元与单位元的素环.假设f:R→R是满射,k=2,3.证明了,f满足[f(x),f(y)]_k=[x,y]_k=[[x,y]_(k-1),y]对所有元x,y∈R成立当且仅当存在映射μ:R→C和元λ∈C使得f(x)=λx+μ(x)对所有元x∈R成立,其中λ~(k+1)=1,C是R的扩展中心.     

富里埃级数|C,1|求和的乘子

本文的主要结果改进了以前所有关于富里埃级数|C,1|求和因子的定理,设f(x)∈L_((-π,π)),f(x)～ΣA_n(x),记φ_x(t)=f(x+t)+f(x-t)-2f(x),其中若则当0<η<ε时级数∑λ_nA_n(x)是|C,1|可求和的,对于共轭级数也有类似的结果。     

学贵有疑--质疑、反思

文[1]“巧解”摘录:题已知二次函数f(x)=ax2 bx c(a,b,c∈R)的图像经过点(-1,0),且x≤f(x)≤12(x2 1)对一切实数x都成立,求f(x).原解设A(x),B(f(x)),C(x2 12)为数轴上的3点,则ABBC=λ.由于当x∈R时,总有x≤f(x)≤12(x2 1)恒成立,∴λ≥0.由定比分点公式得f(x)=x λ(x2 12)1 λ.     

非线性两点边值问题的存在唯一性

对于非线性两点边值问题x″=f(t,x,x′),　x(0)=A,　x(1)=B,我们在f,fx,fx′,β(t),α′(t)都连续,且fx≥-β(t), -α(t)≤fx′≤M(1+|x′|),max β(t)-α2(t)+2α′(t)4t∈[0,1] ≤λ2<π24,α(1)≤2λcotλ,这些条件之下证明解之存在且唯一.     

用定比分点公式巧解一题

题已知二次函数f(x)=ax2 bx c(a,b,c∈R)的图像经过点(-1,0),且x≤f(x)≤12(x2 1),对一切实数x都成立,求f(x).分析本题显然是一道不等式恒成立问题,利用一元二次不等式恒成立知识点来解决,其运算量较大,如果用定比分点公式来解,求解过程就会变得简单、明了.解设A(x),B(f(x)),C(12(x2 1))为数轴上的三点,则ABBC=,λ由于当x∈R时,总有x≤f(x)≤12(x2 1)恒成立,∵λ≥0,由定比分点公式得f(x)=x λ(x2 12)1 λ,又∵曲线y=f(x)经过点(-1,0),∴0=-1 λ1 λλ=1,∴f(x)=14x2 12x 14.本题若结合1≤f(1)≤1 f(1)=1,又f(-1)=0来求解,其运算量也较…     

线段与圆锥曲线的公共点问题探讨

设线段P1P2的两个端点为P1(x1,y1),P2(x2,y2),圆锥曲线G的方程为f(x,y)=Ax2 Bxy Cy2 Dx Ey F=0.则直线P1P2的两点式参数方程为x=x1 λx21 λ,y=y1 λy21 λ其中λ为P(x,y)分有向线段P1P2所成的比,即P1P=λPP2代入f(x,y)=0,并整理化简可得f(x2,y2)λ2 H·λ f(x1,y1)=0(1)其中H=2Ax1x2 B(x1y2 x2y1) 2Cy1y2 D(x1 x2) E(y1 y2) 2F.当f(x2,y2)=0时,P2在曲线G上,方程(1)退化为关于λ的一次方程.当f(x2,y2)≠0时,方程(1)的两根λ1,λ2分别是曲线G与直线P1P2的交点分P1P2所成的比,此时,若f(x1,y1)=0,则P1在曲线G上,方程(1)有一根λ…     

考点3 映射与函数

1.(湖南卷,2)函数f(x)=1-2x的定义域是().(A)(-∞,0](B)[0,+∞)(C)(-∞,0)(D)(-∞,+∞)2.(浙江卷,3)设f(x)=x-1-2,11+x2,x≤1,x>1,则f[f(21)]=().(A)21(B)143(C)-59(D)42153.(山东卷,6)函数f(x)=sin(πx2),ex-1,x-≥1<0.x<0,若f(1)+f(a)=2,则a的所有可能值为().(A)1(B)-22(C)1,-22(D)1,224.(广东卷,11)函数f(x)=11-ex的定义域是.5.(江苏卷,15)函数y=log0.5(4x2-3x)的定义域为.6.(江苏卷,17)已知a、b为常数,若f(x)=x2+4x+3,f(ax+b)=x2+10x+24,则5a-b=.考点3映射与函数1.由1-2x≥0,得x≤0,选(A).2.∵f(12)=-23,∴f[f(21)]=f(-23)=143,故…     

一个无理不等式的类比

文[1]给出了如下不等式:设a,b>0,0<λ≤2,则aa λb bλa b≤21 λ(1)本文给出(1)式的一个类比.定理设a,b>0,0<λ≤3,则3aa λb 3bλa b≤231 λ.(2)证令f(x)=311 λx 131 λx(x>0),则f′(x)=-λ3(1 λx)-43-13(1 λx)-43(-λx2)=-λ3(1 λx)-43 λ3(x λ)-43·x-23,于是,f′(x)     

一类新的增广Lagrange式

1979年,Pillo和Grippo在他们的论文[1]中,研究了等式约束问题min{f(x)|g(x)=0},提出了如下的增广Lagrange式 S_0(x,λ;c)=f(x)+〈λ,g(x)〉+c‖g(x)‖~2+‖M(x)(f(x)+ +g(x)~Tλ)‖~2并得到了局部、全局最优性结果。     

The exact measures of a class of self-similar sets on the plane

Let S (C) R2 be the attractor of the iterated function system{f1,f2,f3}iterating on the unit equilateral triangle So,where fi(x)=λix bi,I=1,2,3,x=(x1,x2),b1=(0,0),62=(1-λ2,0),63=(1-λ3/2,√3/2(1-λ3)).This paper determines the exact Hausdorff measure,centred covering measure and packing measure of S under some conditions relating to the ontraction parameter.     

Uniform boundedness inL p (p=p(x)) of some families of convolution operators

Suppose that a measurable 2π-periodic essentially bounded function (the kernel) κ_λ =κ_λ(x) is given for any realλ≥1. We consider the following linear convolution operator inL ^p: $$\kappa _\lambda = \kappa _\lambda f = (\kappa _\lambda f)(x) = \int_{ - \pi }^\pi {f(t)} k_\lambda (t - x) dt.$$ Uniform boundedness of the family of operators {Κ_λ}_λ≥1 is studied. Conditions on the variable exponentp=p(x) and on the kernel κ_λ that ensure the uniform boundedness of the operator family {Κ_λ}_λ≥1 inL ^p are obtained. The condition on the exponentp=p(x) is given in its final form.     

带有非紧条件的拟线性Schrodinger-Poisson系统非平凡解的存在性

本文研究了如下带有非紧条件的拟线性Schrodinger-Poisson系统{-△u+V(x)u+Фu+k/2u△u2=λ|u|^p-2u+f(u),x ∈R^3,-ΔФ=u^2,x∈R^3, 其中κ<0,λ>0,p≥12,f∈C(R,R),V∈C(R3,R).文中首先构造截断函数,利用集中紧性原理和逼近的方法,得到了截断后系统非平凡解的存在性;然后利用Moser迭代技巧,讨论上述系统非平凡解的存在性.     

On approximation of smooth functions from null spaces of optimal linear differential operators with constant coefficients

For a real valued function f defined on a finite interval I we consider the problem of approximating f from null spaces of differential operators of the form Ln(ψ) = n ∑ k=0 akψ(k), where the constant coefficients ak ∈ R may be adapted to f . We prove that for each f ∈ C(n)(I), there is a selection of coefficients {a1, ,an} and a corresponding linear combination Sn( f ,t) = n ∑ k=1 bkeλkt of functions ψk(t) = eλkt in the nullity of L which satisfies the following Jackson’s type inequality: f (m) Sn(m )( f ,t) ∞≤ |an|2n|Im|1/1q/ep|λ|λn|n|I||nm1 Ln( f ) p, where |λn| = mka x|λk|, 0 ≤ m ≤ n 1, p,q ≥ 1, and 1p + q1 = 1. For the particular operator Mn(f) = f + 1/(2n) f(2n) the rate of approximation by the eigenvalues of Mn for non-periodic analytic functions on intervals of restricted length is established to be exponential. Applications in algorithms and numerical examples are discussed.     

正系数多项式倒数逼近的点态和整体估计

利用Ditzian-Totik光滑模对于[0,1]上定义的非角连续函数f(x)，且f(x)≠0，文中证明存在正系数多项式Pn(x)及常数C，使得|f9x)-1/Pn(x)|≤Cωψ^λ（f,n^-1/2(ψ(x) 1/√n)^1-λ)。当λ＝1时，上述结果导出已有的整体估计，而当0≤λ＜1时，得到倒数逼近一个新的点态局部估计。     

A criterion of vanishing of the spectral density based on homoclinic sums

Let (X, d) be a compact metric space, let T: X→X be a homeomorphism satisfying a certain suitable hyperbolicity assumption, and let μ be a Gibbs measure on X relative to T. Let λ be a complex number |λ|=1, and let f:X → ? be a Hölder continuous function. It is proved that $\sum\limits_{k \in \mathbb{Z}} {\lambda ^{ - k} } \left( {\int\limits_X {f(T^k x)\bar f(x)\mu (dx) - \left| {\int\limits_X {f(x)\mu (dx)} } \right|^2 } } \right) = 0$ if and only if ∑λ^?k(f(T^ky) ? f(T^kx)) = 0 for all x, y ε X such that $d(T^k x,T^k y)\xrightarrow[{|k| \to \infty }]{}0$ . Bibliography: 11 titles.     

指数分布族参数的渐近最优与可容许的经验Bayes估计

在平方损失下 ,构造了指数族 { f(x|λ) =λe-λx,λ >0 ,x >0 }的参数λ的渐近最优与可容许的经验Bayes估计 ,即δn=(n +u + 1n1φ(n) + 1) β1+ βX,其中X1,X2 ,…Xn(历史样本 )和X(当前样本 )独立同分布于 f(x) ,Sn= ni=11n(1+ βXi) ,φ(n) =1n(Sn+ 1n(1+ βX) +v- 1) ,u >0 ,v >0 ,β >0 (已知 )为任意的实数 ,并证明了该估计的收敛速度为O(n- 1)。     

Some estimates of the norm of solutions of nonlinear elliptic eigenvalue problems

We obtain estimates on the possible growth or decay rates as λ → 0 of sup |u^λ|, where uλ ? O satisfies the nonlinear elliptic boundary value problen Lu_λ = λ f(x,u_λ) in a bounded domain subject to homogensous Dirichlet boundary conditions. The estimates generalize existing results by allowing f(x,O) ≠ 0. The analysis is based on integration by parts and Sobolev inequalitie.     

Differential properties and Fourier coefficients of functions of λ-bounded variation

пУстьλ={λ _i} _i=1 ^∞ —пОслЕ ДОВАтЕльНОсть ВЕЩЕс тВЕННых ЧИсЕл сλ _i↑∞ Иλ ^m={λ_т+ i} _i=0 ^∞ . РАссМАтРМВАУтсь 2π-пЕ РИОДИЧЕскИЕ ФУНкцИИ, Дль кОтОРых $$V_\Lambda (f) = \mathop {\sup }\limits_x \mathop {\mathop {\sup }\limits_{(a_i ,b_i ) \cap (a_j ,b_j ) = \emptyset } }\limits_{(a_i ,b_i ) \subset (x,x + 2\pi ]} \mathop \sum \limits_{\iota = 1}^\infty \frac{{\left| {f(b_i ) - f(a_i )} \right|}}{{\lambda _i }}< \infty ,$$ И Дль кОтОРых $$\mathop {\lim }\limits_{m \to \infty } V_{\Lambda ^m } (f) = 0.$$ ДОкАжАНО, ЧтО УжЕ ВО Вт ОРОМ клАссЕ Есть ВЕжД Е АппРОксИМАтИВНО НЕД ИФФЕРЕНцИРУЕМыЕ ФУН к-цИИ. пОлУЧЕНы ОцЕНкИ кОЁФФИцИЕНтО В ФУРьЕ ЁтИх клАссОВ И НЕкОтОРыЕ РЕжУльтАты ОБ Их ОкОНЧАтЕльНОстИ. кАк слЕДстВИЕ ДАНО ДОстА тОЧНОЕ УслОВИЕ Дль Их НЕсОВп АДЕНИь.