,求其定义域。
参考答案:
[解] 这是一个分段函数,定义域为(-∞,∞).
I won’t tell the student the answer to the math problem until he ________ on it for more than an hour.
A.has been working
B.will have worked
C.will have been working
D.had worked
不能用来针对计量资料作统计分析的方法是()。
A.t检验
B.U检验
C.秩和检验
D.泊松分布
E.方差分析