TTGWD4-7

Q7:

If x(x - 5)(x + 2) = 0, is x negative?

(1)     x² – 7x ≠ 0

(2)     x² –2x –15 ≠ 0

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

Answer: C

不太明白，但似乎觉得怎么化减一下就可以得出结论了，脑子慢了，指教一下吧

从题干可以得出x有三个根,0、5、和-2，题目问x是否负就是问x是否等于-2

条件一可得出x不等于0和7

条件二可得出x不等于5和-3

因此可以得出x只能等于-2

thanks a lot