单选题直线ax-by=0与圆x2+y2-ax+by=0(a，b≠0)的位置关系是( )。 A．相交 B．相切 C．相离 D．视a，b的值而定

单选题 Federal Reserve Board Chairman Alan Greenspan laid forth the intellectual basis for the likely continued aggressive easing in monetary policy in the weeks ahead in his semi-annual monetary policy report to Congress. The broader point in his prepared testimony is that the improved information and production controls evident in the new economyinduce companies to respond more quickly and in tandem to changes in their business. Mistakes are still made as is evidenced by the unwanted buildup of inventories at the end of last year, but any mistakes are more aggressively addressed than in the past, as is evidenced by manufacturers' recent slashing of production. Moreover, the increasingly dramatic shifts in economic activity are particularly hard on confidence. Consumers and businesses literally freeze up due to the heightened uncertainty, and run from any perceived risks and curtail their spending and investment. If confidence deflates by enough, then a recession will ensue. Confidence has also been under extraordinary pressure in recent months due to surging energy prices and weaker stock prices. Higher energy bills have acted much like a tax increase, save the checks are largely being written to foreign energy producers. The lower stock prices are having a magnified impact due to the dramatic increase in stock wealth since the mid-1990s. The conduct of monetary policy must adjust to all of this, and thus respond more quickly and aggressively than in the past in an effort to shore up confidence. This explains the dramatic and unprecedented action (at least by a Greenspan-led Federal Reserve) to cut the federal funds rate target by 100 basis points in January: This also suggests that substantially more easing is on the way in the weeks ahead. Just when and by how much will depend on whether confidence continues to fall. The chairman made a point to note that policymakers have significant latitude to ease policy aggressively since inflation remains low and tame. Despite surging energy prices, inflation and inflation expectations remain contained. The Federal Reserve's economic projections for this year provided as part of the testimony support this non-recessionary view. Real GDP is expected to grow by between 2% and 2. 5% between the fourth quarter of 2000 and the fourth quarter of this year. Since this is below the economy's potential growth, the jobless rate will rise to approximately 4. 5% by year's end. Inflation will moderate somewhat in response. Recession risks are rising and as high as they have been since the last downturn almost a decade ago. The key buffer between a soft economy and a recessionary one is confidence, and today's testimony by the Federal Reserve chairman clearly indicates that policymakers will be as aggressive as they need to be to ensure that confidence erodes no further. With just a bit of luck they will succeed.

单选题如图所示，C是以AB为直径的半圆上的一点，再分别以AC和BC为直径作半圆，若AB=5，AC=3，则图中阴影部分的面积是______．

单选题设函数f(x)在(-∞，+∞)内除x=0点外二阶可导，其一阶导数的图形如图所示，则f(x)有______A．两个极大值点，两个极小值点，一个拐点．B．两个极大值点，两个极小值点，两个拐点．C．三个极大值点，两个极小值点，两个拐点．D．两个极大值点，三个极小值点，两个拐点．

单选题实数x，y，z满足条件|x2+4xy+5y2|＝-2y-1，则(4x-10y)z＝()．

单选题设A，B为正定矩阵，C是可逆矩阵，下列矩阵不是正定矩阵的是______．

单选题已知两点P(-2，-2)、Q(0，-1)，取一点R(2，m)使|PR|+|RQ|最小，则m=()．

单选题下列命题中正确的是(A)①、②．(B)①、③．(C)①、④．(D)②、③．

单选题当x取______时，等式恒成立。A．B．C．D．

单选题方程x2+y2-z=0表示的二次曲面是( ) A．椭圆面 B．圆锥面 C．旋转抛物面 D．柱面

单选题将9个人(含甲、乙)平均分成三组，甲、乙分在同一组，则不同的分组方法的种数为______．

单选题m，n和s分别是一个三位数的百位、十位以及个位数，且mns=96，问这个三位数的个位数是多少? (1)这个数是奇数； (2)百位上的数字是8。 (A) 条件(1)充分，但条件(2)不充分． (B) 条件(2)充分，但条件(1)不充分． (C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分． (D) 条件(1)充分，条件(2)也充分． (E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．

单选题曲线y=f(x)如图所示，函数f(x)具有连续的2阶导数，且f'(a)=1，则积分=______。A.a-bB.b-aC.a+bD.ab

单选题已知Rt△ABC的斜边为10，内切圆的半径为2，则两条直角边的长分别为______A．B．C．6和8D．5和7E．