PS：K is one less than product of all the prime intergers,2-23,inclusive, following choices哪几个成立：K可以被2－23中的几个数整除/K可以被30整除/K可以被大于23的某质数整除 然后几个选项正确的是：A:（1）// B:（2）// C:（3）// D:（1）&（2）// E: （2）&（3） 参考答案：(by luckyxmx) 2*3*5*7*11*13*17*19*23-1=223092869 223092869/37=6029537 223092869/131=1702999 所以C是正确的 质数又称素数。指在一个大于1的自然数中，除了1和此整数自身外，没法被其他自然数整除的数。换句话说，只有两个正因数（1和自己）的自然数即为素数 题目中的三个结论：K可以被2－23中的几个数整除/K可以被30整除/K可以被大于23的某质数整除，前两个很容易排除掉是错误的
K and K+1 are two consecutive numbers. So K and K+1 do not share any factors. Since K+1 has factors of all prime numbers no more than 23, then K does not has factors of all the prime numbers between 2 and 23. So K does not have factors between 2 and 23 (because non-prime number can have factors smaller than itself.)
K and K+1 are two consecutive numbers. So K and K+1 do not share any factors. Since K+1 has factors of all prime numbers no more than 23, then K does not has factors smaller than all the prime numbers between 2 and 23. So K does not have factors between 2 and 23 (because non-prime number can factors smaller than itself.)
K and K+1 are two consecutive numbers. So K and K+1 do not share any factors. Since K+1 has factors of all prime numbers no more than 23, then K does not has factors smaller than all the prime numbers between 2 and 23. So K does not have factors between 2 and 23 (because non-prime number can factors smaller than itself.)
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发表于 2011-10-18 09:36:21
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