【数学讨论稿101-200】519起数学讨论稿（更新至200题 5.29 14:58）

sunh0003

hello, no.117, (i)+(ii) there is a case when average =69, there are also cases when average could >70. Hence the answer should be E?

sunh0003

dear, question 162 should be D

sunh0003

dear, also for question 127, i think the answer should be C.

join 2 event = x, did not join 2 event =x
join only one event = 2x. total is 200=x+x+2x. hence x=50 which is the number of people who did not join 2 event

sunh0003

hello, another note, i just realized that for question 176, if x>0 and y<0, it seems that A is the correct answer.
because \x+y\=3 (x>0, y<0), --> then \x-y\ for sure not is equal to 3. am i correct?

sunh0003

jingyang1986 发表于 2016-5-28 06:11
I believe the answer should be D.

for I, agree with you

hello, thanks for your reply. but I still think answer should be A

for II, if x=3, y=-6, then \\x\-\y\\=3 and \x+y\=3, all the other values for x and y, we can get \x+y\=other value. hence only I is sufficient let me know if you have any questions. thanks.

sunh0003

winsontan1818 发表于 2016-5-28 08:16
for that one ..... A,B are the same thing lor.....
lxl=x lyl=-y so lxl-lyl=x+y......

yes.. you are right...i forgot about to simplify the equation..thanks

sunh0003

jingyang1986 发表于 2016-5-28 08:18
OOOOPs, I c where am I wrong.  Thanks for explanation. Then agree with you A

hello, i think i am wrong, i was trying to make an opposite example, but actually you are right, the answer should be D.

sunh0003

hello, 我是198狗主。 写错了一个地方。应该是x<3?  (i)0.025*10^x<25  (ii) 0.025*10^(2x)<250,000 。实在抱歉我记忆力不好。给您造成麻烦了。可以改过来么? 我把我的帖子改过来了。