单选题若正项等比数列an的公比q≠1，且a3，a5，a6成等差数列，则=______。A．B．C．D．

单选题设函数f(x)在点x0的某邻域内可导，且f(x0)为f(x)的—个极小值，则等于

单选题级数的一般项趋于零，即是级数收敛的()。A．充分条件B．必要条件C．充分必要条件D．既非充分也非必要条件

单选题"WHAT'S the difference between God and Larry Ellison?" asks an old software industry joke. Answer: God doesn't think he's Larry Ellison. The boss of Oracle is hardly alone among corporate chiefs in having a reputation for being rather keen on himself. Indeed, until the bubble burst and the public turned nasty at the start of the decade, the cult of the celebrity chief executive seemed to demand bossly narcissism, as evidence that a firm was being led by an all-conquering hero. Narcissus met a nasty end, of course. And in recent years, boss-worship has come to be seen as bad for business. In his management bestseller, "Good to Great", Jim Collins argued that the truly successful bosses were not the serf-proclaimed stars who adorn the covers of Forbes and Fortune, but instead self-effacing, thoughtful, monkish sorts who lead by inspiring example. A statistical answer may be at hand. For the first time, a new study, "It's All About Me", to be presented next week at the annual gathering of the American Academy of Management, offers a systematic, empirical analysis of what effect narcissistic bosses have on the firms they run. The authors, Arijit Chatterjee and Donald Hambrick, of Pennsylvania State University, examined narcissism in the upper levels of 105 firms in the computer and software industries. To do this, they had to solve a practical problem: studies of narcissism have hitherto relied on surveying individuals personally, something for which few chief executives are likely to have time or inclination. So the authors devised an index of narcissism using six publicly available indicators obtainable without the co-operation of the boss. These are: the prominence of the boss's photo in the annual report; his prominence in company press releases; the length of his "Who's Who" entry; the frequency of his use of the first person singular in interviews; and the ratios of his cash and non-cash compensation to those of the firm's second-highest paid executive. Narcissism naturally drives people to seek positions of power and influence, and because great self-esteem helps your professional advance, say the authors, chief executives will tend on average to be more narcissistic than the general population. How does that affect a firm? Messrs Chatterjee and Hambrick found that highly narcissistic bosses tended to make bigger changes in the use of important resources, such as research and development, or in spending and leverage; they carried out more and bigger mergers and acquisitions ; and their results were both more extreme (more big wins or big losses) and more transient than those of firms run by their humbler peers. For shareholders, that could be good or bad. Although (oddly) the authors are keeping their narcissism ranking secret, they have revealed that Mr Ellison did not come top. Alas for him, that may be because the study limited itself to people who became the boss after 1991--well after he took the helm. In every respect Mr Ellison seems to be the classic narcissistic boss, claims Mr Chatterjee. There is life in the old joke yet.

单选题要使α1=(2，1，1)T，α2=(1，-2，-1)T都是齐次线性方程组Ax=0的解，只要系数矩阵A为A．B．C．D．

单选题设复数3+2i的辐角主值为θ，则4-6i的辐角主值是______。A．B．C．D．

单选题满足不等式(x+4)(x+6)+3＞0的所有实数的集合是______．

单选题矩阵的三个特征值是()。A．2，0，0B．1，-1，0C．-1，-1，-1D．2，-1，-1

单选题Onthenumberlineabove,thesegmentfrom0to1hasbeendividedintofifths,asindicatedbythelargetickmarks,andalsointosevenths,asindicatedbythesmalltickmarks.Whatistheleastpossibledistancebetweenanytwoofthetickmarks?

单选题设与都是正项级数，且un≤vn(n=1，2，…)，则下列命题正确的是______A．若收敛，则收敛B．发散，则收敛C．若发散，则发散D．收敛，则收敛

单选题设函数f(x)有连续导数，且，则当f(0)=0时，______

单选题方程z=x 2 +y 2 表示的二次曲面是

单选题函数f(x)=2x 3 -9x 2 +12x-3单调减少的区间为______．

单选题下列求极限问题中洛必达法则失效的是A．B．C．D．

单选题设Dt={(x，y)∈R2|x2+y2≤t2，t＞0}，f(x)为满足的连续函数，则F"(1)=______

单选题设函数则f(x)在(-∞，+∞)内

单选题设函数，则f(1)等于______。

单选题不等式≥2的解集为()．

单选题已知随机变量，则P{X+Y≤1}等于______A．B．C．D．