求值域 y=(x²-1)/(x²+x+1); y=2x-3+√(13-4x); y=(3x+2)/(x-1)

1.y=(x²-1)/(x²+x+1); y导=2x/(x²+x+1)-(x²-1)*(2x+1)/(x²+x+1)^2= [2x*(x²+x+1)-(x²-1)*(2x+1)]/(x²+x+1)^2=(x^2+4x+1)/(x²+x+1)^2,容易得出：在（-2-√3,-∞）上递...