PP-T1-DS78

[max999]

If n is an integer, is -3xn(x的n次方) positive?

(1) x is negative.
(2) n is odd.

answer: C

[smilego]

If n is an integer, is -3xn(x的n次方) positive?

(1) x is negative.
(2) n is odd.


可以看成 -3 (xn)
(1) 如果n是奇數的話, x為負數 所得為positive
如果n是偶數的話, x為正數 所得為negative
1=> n不知 ,不充分
(2) n is odd, x 不知正負數

1+2 => C 為答案