y=(a^x+1)/(a^x-1)
定义域 a^x≠0 x≠1
y*a^x-y=a^x+1
a^x=(y+1)/(y-1)
a^x>0
所以(y+1)/(y-1)>0
(y+1)(y-1)>0
值域 y>1或y