在括号中填上恰当的连词。

①北京____是城市，____它也跟着农村一齐过年，而且过得分外热闹。

②种树人认为，____每天定时浇水，树苗的根____无法深入地下

③____我们是为人民服务的，____我们如果有缺点，就不怕别人批评指出。

数轴上A点表示原点左边距离原点3个单位长度、B点在原点右边距离原点2个单位长度，那么两点所表示的有理数的和是____。

   I  have a good friend．1 name is Peter．We study in Beijing Sunshine Secondary Schoo1．We are in the same(同一个)class．He sits in front of 2 ．His favourite lesson is Music．He  3many CDs．He likes 4 music very much．He likes playing football , t00．After school we  often   play  football in the  5 ．He is very helpful．We often help each 6 ．
   Peter  is  not a Chinese．He is from 7  ．He comes to Beijing 8  his family．His father is  a doctor and his mother is a nurse. They work from Monday    9   Friday．At weekends，his mother  likes shopping and his father likes fishing．Sometimes they go to the park．They all like Chinese  food．They  10   very happy．

计算：

（1）﹣t³•（﹣t）⁴•（﹣t）⁵；                

（2）（b²ⁿ）³（b³）⁴ⁿ÷（b⁵）ⁿ；

（3）t^m+1•t+（﹣t）²•t^m（m为整数）；