(1)
∵对一切x.y>0满足f(x/y)=fx-fy
∴当x=y时f(x/y）=f(x/x）=f(1)=fx-fx=0
∴f(1)=0
(2)
∵f(x/y)=fx-fy
f(x+3)-f(1/x)