单选题设f(x)=2lnx+e x ，则f"(2)=

单选题(E)A、B、C、D都不正确

单选题设y=2-cosx，则y'(0)=( ) A．1 B．0 C．-1 D．-2

单选题设区域D={(x，y)|-1≤x≤1，-2≤y≤2}，则______．

单选题一项复印工作，如果由复印机A，B单独完成，分别需50分钟，40分钟．现两台机器同时工作了20分钟，B机器损坏需维修，余下的工作由A机器单独完成，则完成这项复印工作共需时间______．

单选题不等式lgx+lg(x-3)＜1的解集是( )．

单选题Many video games feature an invincibility power-up that makes the players impervious to damage, at least for a while. As the economic crisis hit in late 2008, some said the same about the industry itself. The theory went that sales of video games, which had been strong in 2008, would also be strong in 2009, because games are a relatively cheap form of entertainment that let people escape from gloomy economic reality. At first glance the sales figures seem to debunk the idea that video games are recession-proof. In June 2009, for example, sales of games in America were 31% lower than in June 2008, according to NPD, a market-research firm. In July sales were down 26% , the fifth successive monthly decline. But the year ended with a record-breaking December, as people bought consoles and games for Christmas. Globally, says Piers Harding-Rolls of Screen Digest, a consuhancy, sales of games were down by 6.3% in 2009. The number of Nintendo Win and Microsoft Xbox 360 consoles sold was flat in 2009 ; sales of Sow's PlayStation 3 were up by 22% after a price cut. In some respects, this stumble reflects gaming's new popularity. When it was less of a mainstream activity it was not so connected to the wider economic cycle. The success of the family-friendly Wii has broadened gaming's appeal, but the new players it has attracted are less fanatical garners who are more likely to cut back in hard times. During 2009 more people turned to mobile, web-based or second-hand games, says Mr Harding-Rofls. Another way of looking at things, however, is to say that spending on gaming is driven by big hits, and that the slight decline in 2009 reflects creative rather than economic weakness. Entertainment industries always have their ups and downs, says Shigeru Miyamoto, the creative force behind many of Nintendo's biggest games. There was an unusually large number of hits in 2008, which boosted sales, and fewer big releases in 2009 until late in the year, which may explain the weak mid-year sales. The biggest hit was "Modern Warfare 2", released in November, which became the fastest-selling game in history, selling 7 million copies worldwide on its first day. The top 20 games took a larger share of sales in 2009 than in 2008, which shows that the games industry is becoming increasingly polarised between hits and misses. Hence the hit-and-miss results of the big publishers of video games. Overall, says Mr Miyamoto, 2009's crop of games may just have been less compelling. "We were not able to produce fun-enough products," he says. That highlights the importance of continued innovation, he says—but it leaves unanswered the question of whether gaming is indeed recession-proof.

单选题设A、B均为n阶矩阵，且(AB)2=E，则下列命题中不正确的是

单选题以下四个命题中，正确的是______

单选题如果等式成立，则函数f(x)=____。

单选题设D为xOy平面上的有界闭区域，z=f(x，y)在D上连续，在D内可偏导且满足在D内没有零点，则f(x，Y)在D上()

单选题某同学在一次数学竞赛中得了93分，共30道题目，如果按照旧的评分方法他只能得到84分，(新的评分方法是答对一道得5分，不答得2分，答错得0分；旧的评分方法是以30分为起点，答对一道得4分，不答得0分，答错扣1分)，在这次竞赛中，该同学没有答的题目有( )道．

单选题设幂级数的收敛半径为3，则幂级数的收敛区间为

单选题设随机变量X～N(0，1)，Y的分布为，且X，Y相互独立．记FZ(z)为Z=XY的分布函数，则FZ(z)的间断点个数为______

单选题函数y=6sinxcosx的最大值为（　）

单选题用电锯把一根长2米的钢材锯成5段，需要24分钟，照这样计算，如果把同样长的钢材锯成7段，需要用( )分钟．

单选题关于x的不等式|3-x|+|x-2|＜a的解集为空集，则实数a的取值范围是( )．

单选题累次积分可写成A．B．C．D．

单选题已知双曲线的中心在原点且一个焦点为(71/2，0)，直线y=x-1与其相交于M，N两点，MN的中点的横坐标为，则该双曲线的方程为______。A．B．C．D．