例4 设A={4,5,6,8}, B={3,5,7,8},求A∪B.
解: A∪B={4,5,6,8} ∪ {3,5,7,8} ={3,4,5,6,7,8}
例5 设集合A={x|-1解: A∪B={x|-1
解: A∪B={x|-1