设函数f(x)=log2X-logx4(0

(1)
f(x)=log2X-logx4=log2X-log2(4)/log2X
=log2X-2/log2X
f(2的an次方)=2n
即log2(2的an次方)-2/log2(2的an次方)=an-2/an=2n
an^2-2n·an-2＝0 （1）
此时2的an次方应该满足函数的定义域,即0