1. **State the problem:** Find the inflection point(s) of the function $$g(x) = \frac{x^2}{2} (9 - 2 \ln(x))$$ and analyze its concavity.
2. **Recall formulas:**
- First derivative: $$g'(x) = \frac{d}{dx} \left( \frac{x^2}{2} (9 - 2 \ln(x)) \right)$$
- Second derivative: $$g''(x) = \frac{d}{dx} g'(x)$$
- Inflection points occur where $$g''(x) = 0$$ and the concavity changes.
3. **Calculate the first derivative using product rule:**
$$g'(x) = \frac{d}{dx} \left( \frac{x^2}{2} \right) (9 - 2 \ln(x)) + \frac{x^2}{2} \frac{d}{dx} (9 - 2 \ln(x))$$
4. **Compute derivatives:**
- $$\frac{d}{dx} \left( \frac{x^2}{2} \right) = x$$
- $$\frac{d}{dx} (9 - 2 \ln(x)) = - \frac{2}{x}$$
5. **Substitute:**
$$g'(x) = x (9 - 2 \ln(x)) + \frac{x^2}{2} \left(- \frac{2}{x} \right) = x (9 - 2 \ln(x)) - x$$
6. **Simplify:**
$$g'(x) = x (9 - 2 \ln(x) - 1) = x (8 - 2 \ln(x))$$
7. **Calculate the second derivative:**
$$g''(x) = \frac{d}{dx} \left( x (8 - 2 \ln(x)) \right) = \frac{d}{dx} (8x) - \frac{d}{dx} (2x \ln(x))$$
8. **Derivatives:**
- $$\frac{d}{dx} (8x) = 8$$
- Use product rule for $$2x \ln(x)$$:
$$\frac{d}{dx} (2x \ln(x)) = 2 \left( \ln(x) + 1 \right)$$
9. **Substitute:**
$$g''(x) = 8 - 2 (\ln(x) + 1) = 8 - 2 \ln(x) - 2 = 6 - 2 \ln(x)$$
10. **Find inflection points by setting $$g''(x) = 0$$:**
$$6 - 2 \ln(x) = 0 \implies 2 \ln(x) = 6 \implies \ln(x) = 3 \implies x = e^3$$
11. **Evaluate concavity:**
- For $$x < e^3$$, say at $$x=1$$:
$$g''(1) = 6 - 2 \ln(1) = 6 - 0 = 6 > 0$$ (concave up)
- For $$x > e^3$$, say at $$x=25$$:
$$g''(25) = 6 - 2 \ln(25) < 0$$ (concave down)
12. **Calculate $$g(e^3)$$ for the inflection point coordinates:**
$$g(e^3) = \frac{(e^3)^2}{2} (9 - 2 \ln(e^3)) = \frac{e^6}{2} (9 - 2 \times 3) = \frac{e^6}{2} (9 - 6) = \frac{e^6}{2} \times 3 = \frac{3 e^6}{2}$$
13. **Final answer:**
- Inflection point at $$\left(e^3, \frac{3 e^6}{2} \right)$$
- Concave up on $$ (0, e^3) $$
- Concave down on $$ (e^3, \infty) $$
This completes the curvature and inflection point analysis for the function $$g(x)$$.
Inflection Point 67Dd46
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