65. 5432-!-item-!-187;#058&004252
If ab ≠ 0 and points (-a, b) and (-b, a) are in the same quadrant of the xy-plane, is point (-x, y) in this same quadrant?
(1) xy > 0
(2) ax > 0
Ans:C
我是算A
因為由題目得知a,b同號:
a,b都>0時 =>第2象限
a,b都<0時 =>第4象限
由(1)可知x,y同號:
x,y都>0時 =>第2象限
x,y都<0時 =>第4象限
單獨充分...
請問是不是有哪裡想錯了??