Asymptotes Critical Points C8Fcf8
1. **Problem Statement:** We are given the function $f(x) = 1 + \frac{1}{x} + \frac{1}{x^2}$ and want to analyze its vertical and horizontal asymptotes, critical points, and inflection points.
2. **Vertical Asymptote:** Vertical asymptotes occur where the function is undefined and the limit tends to infinity. Here, $f(x)$ is undefined at $x=0$ because of division by zero in $\frac{1}{x}$ and $\frac{1}{x^2}$. So, $x=0$ is a vertical asymptote.
3. **Horizontal Asymptote:** To find horizontal asymptotes, analyze the limit of $f(x)$ as $x \to \pm \infty$:
$$\lim_{x \to \infty} \left(1 + \frac{1}{x} + \frac{1}{x^2}\right) = 1 + 0 + 0 = 1$$
$$\lim_{x \to -\infty} \left(1 + \frac{1}{x} + \frac{1}{x^2}\right) = 1 + 0 + 0 = 1$$
Thus, the horizontal asymptote is $y=1$.
4. **Critical Points:** Critical points occur where the derivative $f'(x)$ is zero or undefined (except where the function is undefined).
Calculate the derivative:
$$f'(x) = 0 - \frac{1}{x^2} - \frac{2}{x^3} = -\frac{1}{x^2} - \frac{2}{x^3} = -\frac{x+2}{x^3}$$
Set numerator zero for critical points:
$$x + 2 = 0 \implies x = -2$$
At $x=-2$, $f'(x)=0$, so this is a critical point.
5. **Local Minimum at $x=-2$:** To confirm if $x=-2$ is a local minimum, check the second derivative:
$$f''(x) = \frac{2}{x^3} + \frac{6}{x^4} = \frac{2x + 6}{x^4}$$
Evaluate at $x=-2$:
$$f''(-2) = \frac{2(-2) + 6}{(-2)^4} = \frac{-4 + 6}{16} = \frac{2}{16} = \frac{1}{8} > 0$$
Since $f''(-2) > 0$, $x=-2$ is a local minimum.
6. **Inflection Points:** Inflection points occur where $f''(x) = 0$ or changes sign.
Set numerator of $f''(x)$ zero:
$$2x + 6 = 0 \implies x = -3$$
At $x=-3$, the concavity changes from negative to positive (N shape to U shape), so $x=-3$ is an inflection point.
**Final answers:**
- Vertical asymptote at $x=0$
- Horizontal asymptote at $y=1$
- Local minimum at $x=-2$
- Inflection point at $x=-3$