设函数f（x）=|x+1|+|2x﹣1|的最小值为a．

（1）求a的值；

（2）已知m，n＞0，m+n=a，求$\frac{1}{m}$+$\frac{4}{n}$的最小值．

增加：在缺词处加一个漏子符号（∧）并在其下面写出该加的词。

删除：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1). 每处错误及其修改均仅限一词；

2). 只允许修改10处，多者（从第11处起）不计分。

    My dream school starts at 8:30 a.m. and ends at 3:30 p.m. They are three lessons in the morning and two in the afternoon. We didn't need to do so many homework. Therefore, we have more time with after-school activities. For example, we can do reading for one and a half hour and play sports for one hour every day.

    My dream school look like a big garden. There are all kinds of the flowers and trees around the classroom buildings. We can lie on the grass for a rest, or sat by the lake listening music. The teachers here are kind and helpfully. They are not only our teachers but also our friends.

讠____、____、____      扌____、____、____

辶____、____、____      木____、____、____

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____．