正比例和反比例是描述两种相关联量变化关系的数学概念
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展开图是将一个几何体按照一定的规律展开成一个平面图形的过程。制作展开图时需要注意几何体的各个面之间的连通性和相对位置,以及展开后的图形是否能够完整覆盖几何体的各个面。
Everything is a system, and every system contains systerms.