Practicing Success
The range of the function $f(x)=\frac{x^2+x+1}{x^2+4 x+3}$ is |
(– 1, 2) (– 1, 3) (– 1, 4) none of these |
none of these |
$y=\frac{x^2+x+1}{x^2+4 x+3}⇒y(x^2+4x+3)=x^2+x+1$ $⇒x^2(1-y)+x(1-4y)+1-3y=0$ $f(x) =\frac{x^2+x+1}{x^2+4 x+3} \Rightarrow x^2(1-y)+x(1-4 y)+1-3 y=0$ Since x is real ⇒ discriminant ≥ 0 $\Rightarrow 4 y^2+8 y-3 \geq 0$ $\left.\Rightarrow y \in-\infty, \frac{-2-\sqrt{7}}{2} \cup \frac{-2+\sqrt{7}}{2}, \infty\right)$ Hence (4) is the correct answer. |