1. **Problem statement:** Perform a full curve discussion (Kurvendiskussion) for the function $$f(x) = (x - 1) \cdot (x + 2)^2$$.
2. **Derivative calculation:** Use the product rule: $$f'(x) = (x - 1)' \cdot (x + 2)^2 + (x - 1) \cdot 2(x + 2)$$.
3. Calculate derivatives:
$$ (x - 1)' = 1 $$
$$ f'(x) = 1 \cdot (x + 2)^2 + (x - 1) \cdot 2(x + 2) $$
4. Expand and simplify:
$$ f'(x) = (x + 2)^2 + 2(x - 1)(x + 2) $$
$$ = (x + 2)^2 + 2(x^2 + 2x - x - 2) $$
$$ = (x + 2)^2 + 2(x^2 + x - 2) $$
5. Expand $(x + 2)^2$:
$$ (x + 2)^2 = x^2 + 4x + 4 $$
6. Substitute back:
$$ f'(x) = x^2 + 4x + 4 + 2x^2 + 2x - 4 $$
7. Combine like terms:
$$ f'(x) = (x^2 + 2x^2) + (4x + 2x) + (4 - 4) = 3x^2 + 6x + 0 = 3x^2 + 6x $$
8. Factor derivative:
$$ f'(x) = 3x(x + 2) $$
9. **Symmetry:** The function is neither even nor odd because of the mixed powers and terms.
10. **Zeros of the function:** Solve $$f(x) = 0$$:
$$ (x - 1)(x + 2)^2 = 0 $$
Zeros are at $$x = 1$$ and $$x = -2$$ (with multiplicity 2).
11. **Behavior at infinity:**
As $$x \to \infty$$, leading term dominates: $$f(x) \approx x \cdot x^2 = x^3 \to \infty$$.
As $$x \to -\infty$$, $$f(x) \approx x^3 \to -\infty$$.
12. **Extrema:** Set $$f'(x) = 0$$:
$$3x(x + 2) = 0$$
Solutions: $$x = 0$$ and $$x = -2$$.
13. Determine nature of extrema using second derivative:
Calculate $$f''(x)$$:
$$f''(x) = (3x^2 + 6x)' = 6x + 6$$
Evaluate at critical points:
- At $$x=0$$: $$f''(0) = 6(0) + 6 = 6 > 0$$, so minimum.
- At $$x=-2$$: $$f''(-2) = 6(-2) + 6 = -12 + 6 = -6 < 0$$, so maximum.
14. **Wendepunkte (inflection points):** Solve $$f''(x) = 0$$:
$$6x + 6 = 0 \Rightarrow x = -1$$.
15. Calculate $$f(-1)$$ for inflection point:
$$f(-1) = (-1 - 1) \cdot (-1 + 2)^2 = (-2) \cdot (1)^2 = -2$$.
16. **Summary:**
- Zeros: $$x = -2$$ (double root), $$x = 1$$
- Extrema: max at $$x = -2$$, min at $$x = 0$$
- Inflection point at $$(-1, -2)$$
- Behavior at infinity: $$f(x) \to \infty$$ as $$x \to \infty$$, $$f(x) \to -\infty$$ as $$x \to -\infty$$.
Kurvendiskussion Ecd029
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