(负根号2,-0.5)具体解答:令y=b/(a-1);则显然y<0.....(1)由f(a)=f(b)得b=sqrt(2-a^2),于是y=sqrt(2-a^2)/(a-1).两边平方,整理得:(y^2+1)a^2-2y^2 a+y^2-2=0,进而a=(y^2-sqrt(y^2+2))/(y^2+1)又-1y^2-sqrt(y^2+2)<0.....(2)2y^2-sqrt(y^2+2)>-1....(3)解(1)(2)(3)即得结果。(-sqrt(2),-1/2)