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请教一道数学题

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楼主
发表于 2009-4-1 23:53:00 | 只看该作者

请教一道数学题

If x and y are integers, is y an even integer?

(1)     2yx = x2y2

(2)     x is an odd integer.

                  

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.

答案是A

我选了C

搞不明白[1]是怎么能求出来Y是偶的整数的.......请求帮忙解决,十分感激

沙发
 楼主| 发表于 2009-4-2 23:36:00 | 只看该作者

还有一题不太明白:

If $1,000 will be deposited in a bank account and I is the dollar amount of interest earned from the original deposit, represented as I = 1000 {(1 + r/100)n – 1}, and the annual interest rate is r percent, is r > 8 percent?

(1)   The deposit earns a total of $210 in interest in the first 2 years.

(2)     (1 + r/100)2 > 1.15

 

答案是each one is sufficient

 

第一个我知道,可是第二个有点疑问,若要满足r>8,那么
                
(1 + 8/100)2 > 1.166...不是么?这样的话[2]充分么?

不明白,求教高手....

 

 

板凳
发表于 2009-4-2 23:58:00 | 只看该作者
1.整理下2y+y*y=x*x+x,等式右边,无论X奇数偶数,必定是偶数(奇+奇或偶+偶),等式左边,2Y是偶数,所以y*Y必定偶数,所以可以断定Y是偶数
地板
发表于 2009-4-3 00:03:00 | 只看该作者
2.同意楼主说法,确定答案是C?这个我以前也做到过,没有错呀
5#
 楼主| 发表于 2009-4-6 14:45:00 | 只看该作者

我今天在模考软件上做到这道题目了,答案确实是A,  GWD上答案错了,呵呵

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