1. **State the problem:** Sketch the graph of the function $f(x) = -x^2 - 3x - 2$.
2. **Domain:** The domain of any quadratic function is all real numbers, so $\text{Domain} = (-\infty, \infty)$.
3. **Limits at the endpoints and asymptotes:** Since the function is a polynomial, there are no vertical or horizontal asymptotes.
As $x \to \pm \infty$, $f(x) \to -\infty$ because the leading coefficient is negative.
4. **First derivative:** Calculate $f'(x)$ to find critical points and increasing/decreasing intervals.
$$f'(x) = \frac{d}{dx}(-x^2 - 3x - 2) = -2x - 3$$
Set $f'(x) = 0$ to find critical points:
$$-2x - 3 = 0 \implies -2x = 3 \implies x = -\frac{3}{2}$$
5. **Second derivative:** Calculate $f''(x)$ to determine concavity.
$$f''(x) = \frac{d}{dx}(-2x - 3) = -2$$
Since $f''(x) = -2 < 0$, the graph is concave down everywhere.
6. **Variation table:**
- For $x < -\frac{3}{2}$, $f'(x) = -2x - 3 > 0$ (since $-2x$ is positive and dominates), so $f$ is increasing.
- For $x > -\frac{3}{2}$, $f'(x) < 0$, so $f$ is decreasing.
Thus, $x = -\frac{3}{2}$ is a maximum point.
7. **Intercepts:**
- **y-intercept:** Set $x=0$:
$$f(0) = -0 - 0 - 2 = -2$$
- **x-intercepts:** Solve $f(x) = 0$:
$$-x^2 - 3x - 2 = 0 \implies x^2 + 3x + 2 = 0$$
Factor:
$$ (x + 1)(x + 2) = 0 \implies x = -1, -2$$
8. **Supplementary points:** Calculate $f(-1.5)$ (vertex):
$$f\left(-\frac{3}{2}\right) = -\left(-\frac{3}{2}\right)^2 - 3\left(-\frac{3}{2}\right) - 2 = -\frac{9}{4} + \frac{9}{2} - 2 = -2.25 + 4.5 - 2 = 0.25$$
9. **Sketch the curve:**
- The parabola opens downward (concave down).
- Vertex at $\left(-\frac{3}{2}, 0.25\right)$ is the maximum point.
- Crosses the x-axis at $x = -1$ and $x = -2$.
- Crosses the y-axis at $y = -2$.
Final answer: The graph is a downward-opening parabola with vertex at $\left(-\frac{3}{2}, 0.25\right)$, x-intercepts at $-1$ and $-2$, and y-intercept at $-2$.
Parabola Sketch 41Bbe7
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