4月jj 30题

chengxiao88

30．K^2/8 余几？
A) k/2余1
B） k/3 余2
我选E

我觉得选D

A---> k=2n+1 ---> k^2=4n^2+4n+1 = 4n(n+1)+1 ---> 不管n为奇数还是偶数， 4n(n+1)都被8整除，所以 K^2/8 余1

B--->k=3n+2 --->k^2=9n^2+6n+4 ---> 9n^2+6n 一定被3整除，所以K^2/8 余1

红颜色B的解释看不明白，我觉得答案是A，不知各位大侠怎么看？

stevegt

shouldn't k^2 = 9*n^2 + 12 n + 4?

smalllittle

When n = 1, k^2 = 9 + 12 + 4 = 25 = 3 * 8 + 1, when n = 2, k^2 = 36 + 24 + 4 = 64 = 8 * 8

I think the answer is A...

chengxiao88

i got it,thanks !!!!!!!!!!