【数学讨论稿】鳩耳耳数学讨论稿201-300

weekend55

pinghulinbo 发表于 2015-10-1 12:38
我也问了。。。他回复让我看#17； = = 不明白什么意思

就是让你看一下17楼 之前有人问过 楼主已经解答了      

michelle99bb

Question 212:

I think the answer should be 300 instead of 305 since if we substitute 300 for x in the formular, we will have 10 as the value for Y, greater than 0 when taking 305 for x instead

michelle99bb

Can't understand Q215, can you please explain more? how you get y=1/2? or can you draw a picture please? Many thanks.

lulu178101

225答案是不是有问题，x=-4或2代入原式 等式两边不等吧

janeyang170

michelle99bb 发表于 2015-10-1 13:46
Question 212:

I think the answer should be 300 instead of 305 since if we substitute 300 for x in t ...

212的答案是对的。这个是抛物线，有3种方法求解：
1）讨论君用求导的方法做的；
2）用抛物线对称轴的公式 -(b/2a)可得出x=305时，该抛物线有最大值；
3）可以直观地看出该方程有两个解，x=10；x=600，抛物线对称轴在两个解的中间，即x=(10+600)/2时得到y的最大值为0.

janeyang170

michelle99bb 发表于 2015-10-1 14:01
Can't understand Q215, can you please explain more? how you get y=1/2? or can you draw a picture ple ...

215题应该是狗主没回忆清楚，跟36题是一样的~

janeyang170

讨论君辛苦了~
请问什么时候会继续更新~原始稿出到301题了哈~谢谢~~~

Penspinner

janeyang170 发表于 2015-10-1 15:54
讨论君辛苦了~
请问什么时候会继续更新~原始稿出到301题了哈~谢谢~~~

Updated to 277 now

zyypanda

Penspinner 发表于 2015-9-28 16:29
If x=3, y is also equal to 3

感觉C选项应该是x乘以根号3，而不是根号下3x。所以这个应该是对的。只有0，0满足条件。

janeyang170

Penspinner 发表于 2015-10-1 18:01
Updated to 277 now

多谢晒~~辛苦lar~