题目

若函数y=的定义域为R,则k的取值范围是______________. 答案：解析：由题意可知,对x∈R,kx2-6kx+k+8≥0恒成立,当且仅当解得0≤k≤1.答案:［0,1］. I asked two people the way to the station, but ________ of them could help me． [　　] A．both B．neither C．either D．all