Find the range of f(x)=x2+x+1x2−x+1f(x) = \frac{x^2+x+1}{x^2-x+1}f(x)=x2−x+1x2+x+1.
[1/3,3][1/3, 3][1/3,3]
[0,1][0, 1][0,1]
(0,∞)(0, \infty)(0,∞)
All real numbers