设a为常数，讨论方程x2=aex的实根的个数及每个根所在的范围．

问题问答题

设a为常数，讨论方程x²=ae^x的实根的个数及每个根所在的范围．

答案

参考答案：原方程等价于x²e^-x=a，令F(x)=x²e^-x，则原方程实根的个数与曲线y=F(x)和直线y=a的交点个数相同．函数F(x)的定义域为(-∞，+∞)，且F’(x)=x(2-x)e^-x．列表如下：

选择题

--- Have we ______ water?

--- Yes, _____. We’d better get some.

A．run out of; we have run it out

B．run out of; our water has run out

C．run out of; our water has been run out

D．run out; our water has been run out.

判断题

我国坚持的是积极防御的军事战略方针。