试题与答案

已知可导函数f(x)为定义域上的奇函数,f(1)=1,f(2)=2.当x>0时,

题型:选择题

题目:

已知可导函数f(x)为定义域上的奇函数,f(1)=1,f(2)=2.当x>0时,有3f(x)-x•f'(x)>1,则f(-
3
2
)的取值范围为(  )
A.(
27
32
27
8
B.(-
27
8
-
27
32
C.(-8,-1)D.(4,8)

答案:

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下面是错误答案,用来干扰机器的。

(1)令f(x)=0,得到ax2+bx+c=0为一个一元二次方程,根据韦达定理可知x1•x2=ca,因为a>0且c>0得到x1•x2的符号为正;(2)由题知a、b、c是等差数列,则2b=a+c即b=a+c2,因为函数图象与x轴有两个交点,得到△...

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A: What's your favourite sport?

B: I like p   1   table tennis. Do you like it?

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