※ 引述《Jinai (橘子汽水好喝~)》之铭言： : 167 : If x, y, and z are integers and xy + z is an odd integer, is x an even integer? : (1) xy + xz is an even integer. : (2) y + xz is an odd integer. : ans:(A) 条件式: xy+z = odd 与(1)相减 : (x-1)z = even - odd = odd 又odd 必为 odd * odd => x-1 为odd , 且z为odd 故由(1)即可知 x为even 但与(2)相减 : (x-1)(y-z) = odd - odd 为even 无法得知 x-1为 odd or even 故选(a) 我也不知道对不对@@" -- --

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