若(x+k)(x-4)的积中不含有x的一次项,则k的值为______.
(x+k)(x-4)=x2+(k-4)x-4k,
∴k-4=0,即k=4.
故答案为:4.
患者,女,44岁。素有高血压病史,近两周发现项下不适,可触摸到肿块。诊断为甲状腺瘤。首选药物是()
A.蒲公英
B.夏枯草
C.连翘
D.玄参
E.龙胆
An analyst does research about the coefficient of covariance and the Sharpe ratio. A security's mean return is positive and more than its standard deviation of returns. If the risk-free rate is zero, the coefficient of covariance is most likely:
A. less than the Sharpe ratio.B. equal to the Sharpe ratio.C. greater than the Sharpe ratio.