题目内容：

① y=(x^2-2x+3)/(x^2+x+1)
② y=(3-sin(x))/(2-cos(x))

优质解答

1.设(x^2-2x+3)/(x^2+x+1)=kx^2-2x+3=kx^2+kx+k(1-k)x^2-(k+2)x+3-k=0△=(k+2)²-4(1-k)(3-k)=k^2+4k+4-4k^2+16k-12=-3k^2+22k-8=-3(k-11/3)²-64/3≤0(k-11/3）²≥-64/9 ≥0 -11/3≤k≤11/3值域为 【-...