题干
观察图片，用There be句型介绍图片。（不少于3句话）
答案(点此获取答案解析）
Hello, everyone, this is my classroom. There is a blackboard on the wall. There are eighteen desks and eighteen chairs in my classroom.
观察图片，用There be句型介绍图片。（不少于3句话）
Hello, everyone, this is my classroom. There is a blackboard on the wall. There are eighteen desks and eighteen chairs in my classroom.
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＞0，0＜
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在一个周期内的图象如右图，此函数的解析式为 
