单选题设A为三阶矩阵，为非齐次线性方程组的解，则______．

单选题函数u=xyz2在条件x2+y2+z2=4 (x＞0，y＞0，z＞0)下的最大值是

单选题某商店举行店庆活动，顾客消费达到一定数量后，可以在4种赠品中随机选取2件不同的赠品．任意两位顾客所选的赠品中，恰有1件品种相同的概率是()．

单选题已知A，B均是n阶正交矩阵，A * ，B * 是A，B的伴随矩阵，且|A|=-|B|，则 ①|A+B|=0， ②|A-B|=0， ③|A * +B * |=0， ④|A * -B * |=0 中，正确的结果有______

单选题设A和B为实对称矩阵，且A与B相似，则下列结论中不正确的是______。 A．A-λE与B-λE相似 B．A与B合同 C．|A-λE|=|B-λE| D．A-λE=B-λE

单选题已知三阶行列式，则______。A．-6aB．6aC．-15aD．15a

单选题设z=x3y，则______．

单选题点______是二元函数f(x，y)=x 3 -y 3 +3x 2 +3y 2 -9x的极小值点．

单选题等比数列｛an｝中，已知对于任意自然数n有a1+a2+…+an=2n-1，则a12+a22+…+an2的值为（　）

单选题的值______

单选题设二维随机变量(X，y)的联合密度函数为则k为()

单选题已知a，b是方程x 2 -4x+m=0的两个根，b，c是方程x 2 -8x+5m=0的两个根，则m=______．

单选题设，则F"(1)=______

单选题D(X-3Y+1)=（）

单选题Scientists around the world are racing to learn how to rapidly diagnose, treat and stop the spread of a new, deadly disease. SARS — Severe Acute Respiratory Syndrome — was (1) for the first time in February 2003 in Hanoi, (2) since then has infected more than 1,600 people in 15 countries, killing 63. At this (3) , there are more questions than answers surrounding the disease. Symptoms start (4) a fever over 100.4 degrees F, chills, headache or body (5) . Within a week, the patient has a dry cough, which might (6) to shortness of breath. In 10% to 200% of cases, patients require (7) ventilation to breathe. About 3.5% die from the disease. Symptoms (8) begin in two to seven days, but some reports suggest it (9) take as long as 10 days. Scientists are close to (10) a lab test to diagnose SARS. In the meantime, it is diagnosed by its symptoms. There is no evidence (11) antibiotics or anti-viral medicines help, (12) doctors can offer only supportive care. Patients with SARS are kept in isolation to reduce the risk of (13) . Scientists aren’t sure yet, but some researchers think it’s a (14) discovered coronavirus, the family of viruses that cause some common colds. Most cases appear to have been passed (15) droplets expelled when infected patients cough or sneeze. Family members of infected people and medical workers who care for them have been most likely to (16) the illness. But recent developments in Hong Kong suggest that the (17) might spread through air, or that the virus might (18) for two to three hours on doorknobs or other (19) Health experts say it is (20) , though, that sharing an elevator briefly with an infected person would be enough to pass the virus.

单选题设级数其中α，β，γ均为大于1且与n无关的常数，则______

单选题f(x)=x2+x-1，g(x)=a(x+1)2+b(x-1)(x+1)+c(x-1)2，a，b，c为()时，f(x)=g(x)．

单选题函数的最小正周期是()．

单选题设函数f(u)可导，y=f(x 2 )，当自变量x在x=-1处取得增量Δx=-0.1时，相应的函数增量Δy的线性主部为0.1，则f"(1)=