PP-T1-DS183

[smilego]

183. 18017-!-item-!-187;#058&011390
The positive integers x, y, and z are such that x is a factor of y and y is a factor of z. Is z even?

(1) xz is even.

(2) y is even.

請問這題要如何解呢?? 謝謝

[Huang Hsin-Yi]

z=y*某數=x*某數
(1) xz=even 表示 z有可能是 e or o
when z=e x=o or e
when z=o x=o(此結果與條件不合).....sufficient
(2)y=e不管乘e or o 其z=e.......sufficient