1月30号 jj

steviori

感谢LZ和fatpeng了。

让暴风雨来得更猛烈一些吧。

vear

1. (DS)p is prime?
              A. the only positive factor greater than sqrt(p) is p.
              B. the only positive factor less than sqrt(p) is 1.
B的话 4也符合条件啊

应该是E吧

fatpeng

yes, should be E

steviori

以下是引用fatpeng在2009-1-31 14:21:00的发言：

1. p(x)=ax^2+bx+c, this line are -1 and -3 at zeroes, p(5) is positive?

               i. y intercept is 3

               ii. P(-4)-P(-3) is negative

解：很诡异，由已知p(x)=(x+1)(x+3)=x^2+4x+3, p(5)=48 >0，和条件没有关系啊

peng:

p(x)开口向下是否也行？ 就是p(x)= -x^2-4x-3.

i: 开口向上，p(5)=48>0

II:开口向下，p(5)<0

均可

fatpeng

nice, you are right