新疆
主要內(nèi)容
通過列舉法，詳細(xì)列出集合A={1,2,3,4,5,6,7}的所有128個子集。
一、元素最少和最多的子集情況
元素最少時，即1個元素也沒有，此時有子集A1=?；
元素最多時，即有7個元素，此時有子集A2=A,即：
A2={1,2,3,4,5,6,7}。
二、有1個元素的子集情況
此時個數(shù)為C(7,1)=7個，列舉如下：
A3={1}，A4={2}，A5={3};
A6={4}，A7={5}，A8={6};
A9={7}；
三、有2個元素的子集情況
此時個數(shù)為C(7,2)=21個，列舉如下：
A10={1,2}，A11={1,3}，A12={1,4};
A13={1,5}，A14={1,6}，A15={1,7};
A16={2,3}，A17={2,4}，A18={2,5};
A19={2,6}，A20={2,7}，A21={3,4};
A22={3,5}，A23={3,6}，A24={3,7};
A25={4,5}，A26={4,6}，A27={4,7};
A28={5,6}，A29={5,7}，A30={6,7};
四、有3個元素的子集情況
此時個數(shù)為C(7,3)=35個，列舉如下：
A31={1,2,3}，A32={1,2,4}，A33={1,2,5};
A34={1,2,6}，A35={1,2,7}，A36={1,3,4};
A37={1,3,5}，A38={1,3,6}，A39={1,3,7};
A40={1,4,5}，A41={1,4,6}，A42={1,4,7};
A43={1,5,6}，A44={1,5,7}，A45={1,6,7};
A46={2,3,4}，A47={2,3,5}，A48={2,3,6};
A49={2,3,7}，A50={2,4,5}，A51={2,4,6};
A52={2,4,7}，A53={2,5,6}，A54={2,5,7};
A55={2,6,7}，A56={3,4,5}，A57={3,4,6};
A58={3,4,7}，A59={3,5,6}，A60={3,5,7};
A61={3,6,7}，A62={4,5,6}，A63={4,5,7};
A64={4,6,7}, A65={5,6,7};
五、有4個元素的子集情況
此時個數(shù)為C(7,4)=C(7,3)=35個，列舉如下：
A66={1,2,3,4}，A67={1,2,3,5};
A68={1,2,3,6}, A69={1,2,3,7};
A70={1,2,4,5}，A71={1,2,4,6};
A72={1,2,4,7}，A73={1,2,5,6};
A74={1,2,5,7}, A75={1,2,6,7};
A76={1,3,4,5}, A77={1,3,4,6};
A78={1,3,4,7}, A79={1,3,5,6};
A80={1,3,5,7}, A81={1,3,6,7};
A82={1,4,5,6}, A83={1,4,5,7};
A84={1,4,6,7}, A85={1,5,6,7};
A86={2,3,4,5}, A87={2,3,4,6};
A88={2,3,4,7}, A89={2,3,5,6};
A90={2,3,5,7}, A91={2,3,6,7};
A92={2,4,5,6}, A93={2,4,5,7};
A94={2,4,6,7}, A95={2,5,6,7};
A96={3,4,5,6}, A97={3,4,5,7};
A98={3,4,6,7}, A99={3,5,6,7};
A100={4,5,6,7};
六、有5個元素的子集情況
此時個數(shù)為C(7,5)=C(7,2)=21個，列舉如下：
A101={1,2,3,4,5}, A102={1,2,3,4,6};
A103={1,2,3,4,7}, A104={1,2,3,5,6};
A105={1,2,3,5,7}, A106={1,2,3,6,7};
A107={1,2,4,5,6}, A108={1,2,4,5,7};
A109={1,2,4,5,7}, A110={1,2,5,6,7};
A111={1,3,4,5,6}, A112={1,3,4,5,7};
A113={1,3,4,6,7}, A114={1,3,5,6,7};
A115={1,4,5,6,7}, A116={2,3,4,5,6};
A117={2,3,4,5,7}, A118={2,3,4,6,7};
A119={2,3,5,6,7}, A120={2,4,5,6,7};
A121={3,4,5,6,7};
七、有6個元素的子集情況
此時個數(shù)為C(7,6)=C(7,1)=7個，列舉如下：
A122={1,2,3,4,5,6};
A123={1,2,3,4,5,7};
A124={1,2,3,4,6,7};
A125={1,2,3,5,6,7};
A126={1,2,4,5,6,7};
A127={1,3,4,5,6,7};
A128={2,3,4,5,6,7}。
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