A={1,2,3,4}它的非空真子集的个数是2^4-2=14个分别是:{1},{2},{3},{4}{1,2},{1,3},{1,4},{2,3},{2,4},{3,4}{1,2,3},{1,2,4},{1,3,4},{2,3,4}如果不懂，请Hi我，祝学习愉快！
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