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[数论] 这题有什么好方法

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大佬最帅 posted 2022-3-6 22:25 |Read mode
Screenshot_20220306_222111_com.tencent.mtt_edit_68581985398388.jpg

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爪机专用 posted 2022-3-6 23:34
请码字

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hbghlyj posted 2022-3-6 23:39
建议把标题改成题目的简述...谢谢

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hbghlyj posted 2022-3-6 23:47
设这四个数分别是a、b、c、d,不妨设a>b>c>d,则有:
(a-b)+(a-c)+(a-d)+(b-c)+(b-d)+(c-d)=18
(a-b)+[(a-b)+(b-c)]+[(a-b)+(b-c)+(c-d)]+(b-c)+[(b-c)+(c-d)]+(c-d)=18
3(a-b)+4(b-c)+3(c-d)=18
∴4(b-c)=18-[3(a-b)+3(c-d)]<18
右边是3的倍数,故左边也是3的倍数,由于四个数互不相等,因此(a-b)、(b-c)、(c-d)的值不可能为零,而4(b-c)又是3的倍数,故b-c=3
∴(a-b)+(c-d)=2
由上述讨论知a-b=c-d=1
∴c=d+1,b=d+4,a=d+5
又23100=2^2×3×5^2×7×11
若a<15,则b<14,c<11,d<10,因而abcd<15×14×11×10=23100不合题意;
若a=15,则b=14,c=11,d=10,符合题意;
若a>15,则b>14,c>11,d>10,因而abcd>15×14×11×10=23100不合题意.
故所求四个数为15、14、11、10

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