当x当x<-1时,求f(x)=x^2-3x+1/x+1的值域
当xf(x)=(x^2-3x+1)/(x+1)=[(x^2+2x+1)-5(x+1)+5]/(x+1)=[(x+1)^2-5(x+1)+5]/(x+1)=(x+1)+5/(x+1)-5因为x