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atc

For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive. if p is the smallest prime factor of h(100)+1, then p is
a: between 2 and 10
b: between 10 and 20
c: between 20 and 30
d: between 30 and 40
e: great than 40

[此贴子已经被作者于2007-11-13 1:10:59编辑过]

atc

想明白啦，选e

解：相邻的两个数互质数。h(100)和h(100)+1互质，所以选e.

watermoon07

e

h(100)+1与h(100)互质，所以它们最大公约数是1。也就是说h(100)里的质数因子，h(100)+1都没有。而h(100)的因子是：h(100)=2*4*6*8*10*.......n=2^x*2*3*5*7....*47,所以h(100)+1的最小质数因子一定>47,所以选e.