⑴对任意a，b∈R，a*b=b*a；

⑵对任意a∈R，a*0=a；

⑶对任意a，b∈R，（a*b）*c=c*（ab）+（a*c）+（c*b）﹣2c．

关于函数f（x）=（e^x）* $\frac{1}{e^x}$ 的性质，有如下命题：

⑴f（x）为偶函数；

⑵f（x）的x=0处取极小值；

⑶f（x）的单调增区间为（﹣∞，0；

⑷方程f（x）=4有唯一实根．

其中正确的命题的序号是____．

⑴Did she go to school?____                        A. Of course.

⑵Where is Haikou?____                               B. We went there in June.

⑶What did Daming do yesterday?____       C. It's in the south of China.

⑷When did you go there?____                    D. He climbed the mountain.

⑸Can I make a kite?____                              E. Yes，she did.

I ____ (hurt) myself playing soccer yesterday.

如果关于$x$的方程$a{x}^2+x-1=0$有实数根，则$a$的取值范围是