函数f(x)=x2+ax-3a-9对任意x∈R恒有f(x)≥0，则f(1)=[_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题选择题

函数f(x)=x²+ax-3a-9对任意x∈R恒有f(x)≥0，则f(1)=[ ]

A．6

B．5

C．4

D．3

答案

答案：C

选择题

She knew nothing about his journey _______ he was likely to be away for three months.

A．Except

B．except for

C．except that

D．in addition

单项选择题

临床怀疑蛛网膜下腔出血应采用：（）

A.增强扫描

B.平扫

C.快速CT扫描

D.螺旋CT扫描

E.动态扫描