用判别式法求y=(x^2-x+1)/(x^2+x+1)

用判别式法求y=(x^2-x+1)/(x^2+x+1)
用判别式法求y=(x^2-x+1)/(x^2+x+1)

用判别式法求y=(x^2-x+1)/(x^2+x+1)
y=(x^2-x+1)/(x^2+x+1)
x^2-x+1=y(x^2+x+1)
即(y-1)x^2+(y+1)x+(y-1)=0
上诉方程有解
则y=1时 x=0满足
y不等于1时 判别式=(y+1)^2-4(y-1)^2>=0
得1/3