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ãËé n à»ç¹ÊÁÒªÔ¡¢Í§à«µ {1,2,3,....,3000} ¨§ËÒ¼ÅÃÇÁ¤èÒn ¶éÒ 2 ËÒÃnäÁèŧµÑÇ ËÃ×Í 3 ËÒà n äÁèŧµÑÇ ¾ÔÁ«Ô¡ÁÒäÁèà»ç¹ÍèФÃѺ¢Íâ·É´éǹФÃѺ
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ãËé ૵ $X = {{1,2,3,...,3000}} $
$A $¤×Í૵¢Í§ $n \in X «Öè§ 2\mid n$ $B$ ¤×Í૵¢Í§$ n \in X «Öè§ 3\mid n$ $(\left|A\cap B\,\right|)' = U- \left|A\cap B\,\right|$ $\left|A\cap B\,\right| = ૵¢Í§ n\in X «Öè§ 6\mid n $ ¼ÅÃÇÁ¢Í§ ¨Ó¹Ç¹·ÕèËÒà 2 ËÃ×Í 3 äÁèŧ = $\frac{(3000)(3001)}{2} - \frac{(3000)(501)}{2} $ |
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#3,4. Íѹ¹Ñ鹤×Í 2áÅÐ3ËÒÃäÁèŧµÑǤÃѺ ÇÔ¸Õ·Ó·ÓẺ#2
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