分类：教育/科学-学习帮助
问题：求函数值域的题函数y=log0.5(x+1/x
y=log0.5(x+1/x-1+1)(x>1)的值域是多少?A(-无穷,2] B(-无穷,-2] C[2,+无穷) D[-2,+无穷)写出本题用到求值域的哪种方法并写出详细的分析和解题过程
回答：x+1/(x-1)+1=(x-1)+1/(x-1)+2>=4
y=log(0.5)t是单调减函数
y<=log(0.5)4=-2
值域是(-无穷,-2]
选B