共查询到20条相似文献,搜索用时 62 毫秒
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题目 已知当x∈[0,1]时,不等式x2cosθ-x(1-x)+(1-x)2sinθ>0恒成立,试求θ的取值范围.这是1999年全国高中数学联合竞赛试题第三题,下面给出一种有别于“标准答案”的简单解法.解 若对一切x∈[0,1],恒有f(x)=x2cosθ-x(1-x)+(1-x)2sinθ>0,则 sinθ=f(0)>0,cosθ=f(1)>0,∴ 2kπ<θ<2kπ+π2,k∈Z.(1)又 f(x)=(1+sinθ+cosθ)x2-(1+2sinθ)x+sinθ=(1+sinθ+cosθ)[… 相似文献
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本文用数形结合的方法,求解形如:f(x)=m+nx-x2-p+qx-x2(n2+4m>0,q2+4p>0)的函数的最值,此函数的定义域非空.设方程m+nx-x2=0的两根为a、b,且a<b;设p+qx-x2=0的两根为c、d,且c<d.则a=n-n2... 相似文献
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本文考虑了亚纯函数的幅角分布及其增长性的关系,得到了如下定理:设f(z)为亚纯函数,下级μ(μ〈+∞,argz=θk(k=1,2,…,q;0≤θ1〈θ2〈…〈θq〈2π,θq+1=θ1+2π)为q(1≤q〈+∞)条半直线使对A↓ε〉0有:limr→∞↑-log+n↑-(∪k=1↑qΩ↑-(θk+ε,θk+1-ε;r),f=x)/logr≤ρ〈+∞ x=0,∞则当存在一非负整数l使f^(l)(z)( 相似文献
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Poisson分布参数的渐近最优和可容许的经验Bayes估计 总被引:2,自引:0,他引:2
设X及(X1,X2…,Xn)分别为取自Poisson分布P(θ)的当前样本和历史样本,参数θ的先验分布族F={Γ(m,β):β>0},其中m>0已知,Γ(m,β)表示参数为(m,β)的伽玛分布.对p>0,q>2的任意两个实数,记tn=X+∑ni=1Xi+pX+∑ni=1Xi+p+q+(n+1)m(X+m)则在平方损失函数l(θ,d)=(θ-d)2下,tn是θ的渐近最优和可容许的经验Bayes估计,而且收敛速度为O(1n). 相似文献
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设d无平方因子,h(d)是二次域Q(d)的类数,本文证明了:若1+4k2n=da2,a,k>1,n>2为正整数,且a<0.9k35n或n的奇素因子p和k的素因子q均适合(p,q-1)=1,则除(a,d,k,n)=(5,41,2,4)以外,h(d)≡0(modn).同时,我们猜测:上述结果中的条件(p,q-1)=1是不必要的. 相似文献
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一个反应扩散过程的门槛结果 总被引:3,自引:0,他引:3
本文讨论反应扩散方程Cauchy问题(ut-△u=u^p-u^p-u,X∈R^n,t∈(0,T),u(x,0)=u0(x)≥0,X∈R^n,解的整体存在性,渐近性质和Blow-up问题,其中1<q<p<n+2/n-2,n≥3或者1<q<p+∞,n=2.得到门槛结果。 相似文献
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本文证明了当b∈BMO时,具有弱核的CalderónZygmund奇异积分算子的交换子[b,T]f=bT(f)-T(bf)是Lp(1<p<∞)有界的.一个等价的命题是双线性算子gT(f)-fT(g)∈H1,只要f∈Lp,g∈Lq,1<p<∞,1p+1q=1. 相似文献
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Jacobi多项式零点为结点的Lagrange插值多项式之逼近 总被引:1,自引:0,他引:1
对于可微函数f∈Cq[-1,1],本文研究以Jacobi多项式J(α,β)n(x)的零点为结点组之Lagrange插值多项式对f及其导数的同时逼近,证明不等式L(s)n(f,α,β,x)-f(s)(x)=O(1)Δ-sn(x)Δqn(x)ω(f(q),Δn(x))logn{+(1-x+n-1)-α-12n-qω(f(q),n-1)},在[0,1]上对于s=0,1,2,…,q一致成立,其中Δn(x)=n-11-x2+n-2 相似文献
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文[1]介绍了1997年高考(理科)24题的命题思想,其最初形式为给定二次多项式f(x)=ax2+bx+c,a>0,设0<x1<x2<1a,满足f(xi)=xi,i=1,2,证明:当0<x<x1时,(1)x<f(x)<x1;(2)存在0<q<1,使得... 相似文献
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In this article, we study positive solutions to the system{A_αu(x) = C_(n,α)PV∫_(Rn)(a1(x-y)(u(x)-u(y)))/(|x-y|~(n+α))dy = f(u(x), B_βv(x) = C_(n,β)PV ∫_(Rn)(a2(x-y)(v(x)-v(y))/(|x-y|~(n+β))dy = g(u(x),v(x)).To reach our aim, by using the method of moving planes, we prove a narrow region principle and a decay at infinity by the iteration method. On the basis of these results, we conclude radial symmetry and monotonicity of positive solutions for the problems involving the weighted fractional system on an unit ball and the whole space. Furthermore, non-existence of nonnegative solutions on a half space is given. 相似文献
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Reza Mazrooei-Sebdani 《Communications in Nonlinear Science & Numerical Simulation》2012,17(10):3857-3865
Consider the following system of rational equations containing quadratic termsChaos in the sense of Li–Yorke is considered. This is based on the Marotto’s theorem via obtaining a snap-back repeller. In fact, first in a special case when , we show that origin is a snap-back repeller and so the system has chaotic behavior in the sense of Li–Yorke under some conditions. Then in a more general case, we prove that existence of chaos in the sense of Li–Yorke for the above system. 相似文献
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We consider the system of nonlinear wave equations with initial and Dirichlet boundary conditions. Under some suitable assumptions on the functions, , , , parameters and the initial data, the result on blow-up of solutions and upper bound of blow-up time are given. 相似文献
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We consider the fractional Hartree equation in the -supercritical case, and find a sharp threshold of the scattering versus blow-up dichotomy for radial data: If and , then the solution is globally well-posed and scatters; if and , the solution blows up in finite time. This condition is sharp in the sense that the solitary wave solution is global but not scattering, which satisfies the equality in the above conditions. Here, Q is the ground-state solution for the fractional Hartree equation. 相似文献
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