1、集合A为7个元素，列举该集合的全部子集。
3、有2个元素的子集情况，此时个数为C(7,2)=21个，A10={5,-8}，A11={5,11}，A12={5,-14};帆歌达缒A13={5,17}，A14={5,-20}，A15={5,23};A16={-8,11}，A17={-8,-14}，A18={-8,17};A19={-8,-20}，A20={-8,23}，A21={11,-14};A22={11,17}，A23={11,-20}，A24={11,23};A25={-14,17}，A26={-14,-20}，A27={-14,23};A28={17,-20}，A29={17,23}，A30={-20,23};
9、A111={5,11,-14,17,-20}, A112={5,11,-14,17,23};A113={5,11,-14,-20,23}, A114={5,11,17,-20,23};A115={5,-14,17,-20,23}, A116={-8,11,-14,17,-20};A117={-8,11,-14,17,23}, A118={-8,11,-14,-20,23};A119={-8,11,17,-20,23}, A120={-8,-14,17,-20,23};A121={11,-14,17,-20,23};
