(1)令2^x=t,则2t/(t+1)=1/2,解得t=1/3,即2^x=1/3,即x=-log2#3
(2)t>0,y=2t/(t+1),t=y/(2-y)>0,即y(y-2)
（1）解：f（x）=2^（x+1）／2^x+1=1／2.（2）f（x）值域.
(1)令2^x=t,则2t/(t+1)=1/2,解得t=1/3,即2^x=1/3,即x=-log2#3
(2)t>0,y=2t/(t+1),t=y/(2-y)>0,即y(y-2)