壹贰贰玖，遛狗狗，尴尬的准备二战 ~更新完毕~

sdcar2010

DS：问N是不是differences of two prime numbers
（1）N=11
（2）(N-7)(N-11)=0
这题我不会做，蒙的


(1) is sufficient. 2 and 13
(2) is sufficient.  Since the difference cannot be 7.  2+7 =9 and 9 is not prime.  Then the difference has to be 11.

Choose D.

-- by 会员 sdcar2010 (2010/12/29 23:07:34)

不对吧 应该是A……问N是不是两个质数的差 （2）中N=7或11， 当N=7是不行，但当N=11时可以，所以不能确定到底行不行

-- by 会员 sharronhe (2010/12/29 23:22:16)

You are right.  I will fix it.

曲宁儿

LZ, keep up the good work and you will get 700+ scores in GMAT.

-- by 会员 sdcar2010 (2010/12/29 23:15:24)

Thanks! I'll keep working and do it again in early Feb!

Thanks again for all the help in math! Btw, add me as your friend in this forum, I've already sent the request, accept it plz! ^^

scauhyl

lz  h rp

曲宁儿

lz  h rp

-- by 会员 scauhyl (2010/12/29 23:46:50)

我竟然看懂了…… 哈哈~ 谢谢~

AlohaDJ

If r@s=s@r, then which of the following is true? @代表符号，没记错的话应该是这样，这题我也完全没头绪
I. r@s = r + s -rs
II. r@s = (r+s)(r-s)
III. r@s = s/r + r/s
选项是什么I,II or I, III, or...or 全部

1 is right
2 is not
3 is right.

Choose I, III


由r@s=s@r,可知@符号代表加号或乘号，然后分别验证3个选项，可否这样考虑？可这样考虑结果为None.
NN能否详解下。。没头绪ing...THKS!!

曲宁儿

楼上的MM请看第一页最后一楼，我做题时的思路和你一样，也认为是none，但是这题没有none这个选项~

小困蛇

辛苦了，积极讨论

WIWMM

A也不可以吧   例如16-5=11  但是16不是质数