求讨论. 第二百二十七题 k,m是整数,k is a factor of m,is m/k even? 1) km is even 2) k+m is odd (提供者ID:稀饭zxp。选B还是选C来着,脑子拧不过来了) 选B 我是代具体数值. 希望有大牛提供更好的思路 (1) km is even..=> k odd, m even or k even, m even or k even, m odd 但是 k is a factor of m. 所以只可能是 k even, m even or k even, m odd 假设 k even, m even => k=2 m=6 则 m/k=odd k even, m odd => k=3 m=6 则 m/k=even 所以(1)不充分 (2) k+m is odd => m is odd, k is even 没有数值能满足条件. 不成立 or m is even, k is odd. m=6 k=3 => m/k=2 even 所以只有(2)充分 选B -- by 会员 merrymenglu (2012/3/11 16:28:20)
思路:
条件一:mk为偶数,则
1.m为偶数,k=2 ,m/k不一定为偶数
2.m为偶数,k ≠2,m/k为偶数
条件二:k+m isodd ,K,m 为一奇数,一偶数。
因为k 为因子,只能是m 为偶数, k奇数.k不等于2 m/k 为偶数 . 答案:B
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