Stationary Points 7Ee20E
1. **Problem statement:** Find and classify all stationary points of the function $$f(x) = x^3 - 6x^2 + 9x + 2$$.
2. **Find stationary points:** Stationary points occur where the first derivative $$f'(x)$$ equals zero.
Given $$f'(x) = 3x^2 - 12x + 9$$, set it to zero:
$$3x^2 - 12x + 9 = 0$$
3. **Solve the quadratic equation:** Divide both sides by 3:
$$x^2 - 4x + 3 = 0$$
Factor:
$$(x - 3)(x - 1) = 0$$
So, $$x = 1$$ or $$x = 3$$.
4. **Classify stationary points using the second derivative:**
Calculate $$f''(x)$$:
$$f''(x) = \frac{d}{dx}(3x^2 - 12x + 9) = 6x - 12$$
Evaluate at $$x=1$$:
$$f''(1) = 6(1) - 12 = -6 < 0$$, so $$x=1$$ is a local maximum.
Evaluate at $$x=3$$:
$$f''(3) = 6(3) - 12 = 6 > 0$$, so $$x=3$$ is a local minimum.
5. **Find the function values at stationary points:**
$$f(1) = 1 - 6 + 9 + 2 = 6$$
$$f(3) = 27 - 54 + 27 + 2 = 2$$
---
6. **Second-order partial derivatives:** The function $$f(x)$$ is a single-variable function, so second-order partial derivatives do not apply here.
**Final answer:**
- Stationary points at $$x=1$$ (local maximum, $$f(1)=6$$) and $$x=3$$ (local minimum, $$f(3)=2$$).
- No second-order partial derivatives since $$f$$ is a function of one variable.