(2)f(x)=2x/(x+2)
f(x)+f(m-x)
=2x/(x+2)+2(m-x)/(m-x+2)
=n
令x=0,则2m/(m+2)=n
令x=-1,则2(m+1)/(m+3)=n+2
解得:m=-4,n=4
∴f(x)+f(-x-4)
=2x/(x+2)+2(x+4)/(x+2)
=4
(2)f(x)=2x/(x+2)
f(x)+f(m-x)
=2x/(x+2)+2(m-x)/(m-x+2)
=n
令x=0,则2m/(m+2)=n
令x=-1,则2(m+1)/(m+3)=n+2
解得:m=-4,n=4
∴f(x)+f(-x-4)
=2x/(x+2)+2(x+4)/(x+2)
=4