集合具有概念性强、涉及面广、解法灵活等特点,因而必须对重点知识进行深刻领悟。1.加深对空集“φ”的认识(1)忽视不得的性质: 空集是任何集合的子集,即φ(?)A;对任意集合A,皆有A∩φ=φ,对任意集合A,皆有A∪φ=A。忽略了φ的上述性质,就会导致错解或解题不完善。【例1】已知集合A={x|x~2+x-6=0},B={x|mx+1=0},求m,使B(?)A。 The collection has the characteristics of strong conceptuality, wide coverage, and flexible solution. Therefore, it is necessary to deeply comprehend key knowledge. 1. To deepen the understanding of the empty set “φ” (1) To ignore the obligatory properties: The empty set is a subset of any set, ie φ(?)A; for any set A, there are A∩φ=φ, for arbitrary Set A, all have A∪φ=A. Ignoring the above properties of φ leads to misunderstanding or incomplete problem solving. [Example 1] Known set A={x|x~2+x-6=0}, B={x|mx+1=0}, find m so that B(?)A.