设p=(log2x)2+(t-2)log2x-t+1,若t在区间[-2,2]上变动时,p恒为正值,试求x的取值范围.

问题描述:

设p=(log2x)2+(t-2)log2x-t+1,若t在区间[-2,2]上变动时,p恒为正值,试求x的取值范围.

p=(log2x-1)t+(log2x)2-2log2x+1,∵t∈[-2,2]时p恒为正值,

-2(log2x-1)+(log2x)2-2log2x+1>0
2(log2x-1)+(log2x)2-2log2x+1>0

解得log2x<-1或log2x>3,
即0<x<
1
2
或x>8.