http://www.google.cn/search?client=aff-cs-360se&ie=utf-8&oe=UTF-8&hl=zh-CN&q=%E9%87%91%E9%92%A5%E5%8C%991%2B1%E4%BA%94%E5%B9%B4%E7%BA%A7%E7%9A%84%E7%AD%94
1+1=2
上学期？
