共查询到20条相似文献,搜索用时 62 毫秒
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根据数列{an}的前n项和Sn与an的关系an=Sn-Sn-1(n∈Z,n≥2)可知,凡是存在通项公式Sn=f(n)的递推公式Sn=a1+a2+…+an-1+an, 相似文献
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我们知道,{αn}是等差数列时,αn=α1+(n-1)d,Sn=nα1+n(n-1)/2d(Sn=αn^2+bn,Sn/n=αn+b(a≠0)).当a≠0时,世,Sn/n是n的一次函数,S是n的二次函数,且不含常数项(n∈N^+). 相似文献
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孙建斌 《中学数学教学参考》2008,(8):56-56
定理 设a,b∈R+,m,n∈N,x∈(0,π/2),则当且仅当x=arctan^2m+n√(b/a)^m时,y=a/cosn/mx+b/sinn/mx有最小值(a2m/2m+n+b2m/2m+x)2m+n/2m. 相似文献
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函数f(x)=a/cos^nx+b/sin^nx最小值猜想的一个初等证明 总被引:3,自引:0,他引:3
王凯成 《中学数学教学参考》2006,(10):51-51
万新灿、郑晓玲老师在文[1]中提出猜想:
f(x)=a/cos^nx+b/sin^nx(0〈x〈π/2,a、b为大于0的常数,n∈N+),当且仅当x=arctan n+2√a/b时,取最小值(a2/n+2+b2/n+2)n+2/2 相似文献
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等差数列的前n项和Sn是关于n的过原点的二次函数,其标准形式为S n=An^2+Bn(A、B∈R),等比数列的前n项和的标准形式为S n=A-Aq^n(A∈R).对于形如(an+b)·q^n(a、b∈R,q≠1)的数列,其前n项和的标准形式为Sn=A+q^n(Bn-A). 相似文献
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李敏 《中学数学研究(江西师大)》2010,(3):36-39
例1 (2009年全国高考陕西卷文21变式)已知数列{an}的前n项和为Sn,满足a1=1,a2=2,Sn+2=Sn+3an+1+an/2,n∈N^*. 相似文献
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《中学数学教学参考》2007,(7):55
文[1]用较大篇幅证明f(x)≥(2/a^n+2+2/b^n+2)n+2/2(a>0,b>0,n∈N(=|x=arctan n+2√a/b) 下面给出两个初等而简捷的证明供大家参考. 相似文献
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文献[1]提出了如下猜想:
猜想f(x)=a/cos^nx+b/sin^nx(0〈x〈π/2,a,b为大于零的常数,n∈N^*)当且仅当x=arctan n+2√b/a时,取到最小值(2/a^n+2+2/b^n+2)^n+2/2. 相似文献
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题1 设a,b∈(0,+∞),且(√b^2+c^2+b-c)(√a^2+c^2+a-c)=2ab,求证:c^2=ab.[第一段] 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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Rajesh Kanoi 《海外英语》2007,(1):52
Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer. 相似文献