填空题已知向量组若β不能由α1，α2，α3线性表示，则n的取值为______．

填空题设函数满足，则

填空题In the following text, some sentences have been removed. For Questions (41-45), choose the most suitable one from the list A-G to fit into each of the numbered blank. There are two extra choices, which do not fit in any of the gaps. Coffee is worth approximately $ 50-60bn each year in terms of world sales. It is a truly international commodity, and today more than 50 countries in the world grow coffee beans. This makes the coffee industry fairly universal, according to Pablo Dubois, head of the International Coffee Organisation (ICO), based in London. ICO organization helps coffee producers and promotes coffee consumption worldwide. ICO estimates that world production next year will reach 97.5 million bags, 11.3 million bags higher than the current year. The main reason for this is higher Brazilian output as production recovers from weather damage to crops. 41．______In 1994 Brazil was responsible for 25% of world production, Colombia was next with 13.4%, Indonesia had 7.5%, Mexico 4.7%, Guatemala 3.8% and Ethiopia and Vietnam were equal with 3.4%. Coffee is a tough crop, and can be grown in areas where it is difficult or impossible to grow other crops. It is cultivated in mountain regions which can only be reached by animal transport, and in other difficult areas where modern agricultural equipment cannot be used. 42． ______ICO is active in educating farmers about avoiding disease and dealing with problems when they occur. The distribution chain varies from country to country, explains Pablo Dubois. In most countries the smaller farmers sell their crop to a local trader, who then sells it on to exporters. 43． ______Larger coffee growers, for example, frequently export directly. Some countries, like Vietnam, have special government marketing organizations for coffee. Coffee prices often vary greatly from one year to the next. In 1997, for example, there was a large rise in the world price, which was immediately felt by the consumer. 44．______ In some of these countries, this can amount to as much as 50% of all export earnings. In the opinion of Pablo Dubois, the biggest problem for his organisation is to create greater consumer awareness of the different varieties of coffee and different ways of preparing it. In North America, most consumers already have above average knowledge Of the range available. 45．______It is also encouraging environmentally friendly coffee production, and last year's seminar on coffee and the environment created a lot of interest. The future looks bright for the coffee industry. It is estimated that consumption over the next few years will continue to rise steadily. New markets like Eastern Europe and China are expected to develop fast. [A] However, disease is always problem for coffee production, as we can see in some parts of South America at the moment. [B] Because the amount of coffee demand is on a high rise. [C] ICO is therefore concentrating its promotional activities on Russia and China. [D] As the largest producing country, Brazil is particularly important in the coffee world. [E] Rising prices always result in a drop in sales, which will have a bad effect on those developing countries, which are highly dependent on foreign exchange from coffee exports. [F] There are, however, other distribution systems. [G] Almost all the coffee growers share the same distribution channel.

填空题函数y=x-ln(1+x)的驻点为x=______

填空题设f(x)连续，且当x→0时，是与x3等价的无穷小量，则f(0)=________．

填空题设在x=0处连续，则a=________．

填空题设A=2a+b，B=ka+b，其中｜a｜=1，｜b｜=2，且a⊥b．若A⊥B，则k=_________．

填空题数列1，，…的最大项为________．

填空题设二元函数f(u，v)可微，则______.

填空题若A=，则A*=________，(A*)*=________．

填空题设区域D由曲线y=x2，y=1围成，则=______．

填空题设函数，则y"=________．

填空题设y=cosx，则y''=______．

填空题设y=y(x)由方程x 2 +xy 2 +2y=1确定，则dy=______．

填空题设D是由x2+y2≤a2，y≥0所确定的上半圆域，则D的形心的y坐标=________。

填空题设(X1，X2，…，Xn，Xn+1，…，Xn+m)为来自总体X～N(0，σ2)的简单样本，则统计量U=服从________分布．

填空题设常数a＞0，则

填空题甲乙两站相距1 950 km，汽车A、B、C分别匀速行驶，汽车A从甲站开向乙站，同时汽车B、汽车C从乙站出发与车A相向而行开往甲站，则能确定途中车A与车B相遇两小时后再与车C相遇． (1)汽车A、B、C分别以每小时80、70、50 km的速度匀速行驶； (2)汽车A、B、C分别以每小时70、60、50 km的速度匀速行驶．

填空题函数f(x)在点x0有定义是极限存在的________条件．