(1)f（x）=(ax+b)/(x^2+1)是奇函数,f(-x)=-f(x)(-ax+b)/(x^2+1)=- (ax+b)/(x^2+1),-ax+b=-ax-b, b=-b,所以b=0.又f(1/2)=2/5,所以(a/2)/(1/4+1)=2/5,a=1.∴f(x)=x/(x^2+1).(2)设任意-1