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标题: GWD-3-05 請問喔 [打印本页]

作者: h5641 时间: 2009-4-9 20:05
标题: GWD-3-05 請問喔

Q5:

If (y+3)(y-1) – (y-2)(y-1) = r(y-1), what
is the value of y?

(1) r²
= 25

(2) r =
5

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:

我的解題:

題目化簡 : (y+3)(y-1) – (y-2)(y-1) = r(y-1) => (y+3) - (y-2) = r

(1) r² = 25, 所以 r =5 or -5

當 r =5, 則可推出 y= -3 時會滿足

r = -5, 無答案

(2) r = 5 時, 則可推知 y= -3

因此我選 (B).

但答案是給 (E) 我不知道自己哪裡忽略了

請高手幫忙指導謝謝~~

作者: fanruifelix 时间: 2009-4-9 20:17

感觉应该是r不等于5时，才能推出y=1

如果r=5，y任何值都满足情况啊。

因为y不等于1时，有（y+3)-(y-2)=y+3-y+2=5=r

作者: h5641 时间: 2009-4-9 20:34
感謝我弄懂了!

謝啦~

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