1. **State the problem:** We want to graph the cubic function $$A(x) = \frac{1}{2} x^3 - \frac{9}{2} x^2 + 9 x$$ defined on the interval $$[0,3]$$.
2. **Understand the function:** This is a cubic polynomial. Cubic functions can have up to two turning points (local maxima or minima) and one inflection point.
3. **Find critical points:** To find turning points, compute the derivative:
$$A'(x) = \frac{d}{dx} \left( \frac{1}{2} x^3 - \frac{9}{2} x^2 + 9 x \right) = \frac{3}{2} x^2 - 9 x + 9$$
4. **Set derivative to zero to find critical points:**
$$\frac{3}{2} x^2 - 9 x + 9 = 0$$
Multiply both sides by 2 to clear fraction:
$$3 x^2 - 18 x + 18 = 0$$
Divide both sides by 3:
$$\cancel{3} x^2 - \cancel{18} x + \cancel{18} = 0 \Rightarrow x^2 - 6 x + 6 = 0$$
5. **Solve quadratic equation:**
$$x = \frac{6 \pm \sqrt{(-6)^2 - 4 \cdot 1 \cdot 6}}{2} = \frac{6 \pm \sqrt{36 - 24}}{2} = \frac{6 \pm \sqrt{12}}{2} = \frac{6 \pm 2 \sqrt{3}}{2} = 3 \pm \sqrt{3}$$
6. **Check if critical points lie in domain [0,3]:**
- $$3 - \sqrt{3} \approx 3 - 1.732 = 1.268$$ (inside domain)
- $$3 + \sqrt{3} \approx 3 + 1.732 = 4.732$$ (outside domain)
Only $$x = 3 - \sqrt{3}$$ is relevant.
7. **Find function values at critical points and endpoints:**
- At $$x=0$$:
$$A(0) = 0$$
- At $$x=3 - \sqrt{3}$$:
$$A(3 - \sqrt{3}) = \frac{1}{2} (3 - \sqrt{3})^3 - \frac{9}{2} (3 - \sqrt{3})^2 + 9 (3 - \sqrt{3})$$
- At $$x=3$$:
$$A(3) = \frac{1}{2} (3)^3 - \frac{9}{2} (3)^2 + 9 (3) = \frac{1}{2} \cdot 27 - \frac{9}{2} \cdot 9 + 27 = 13.5 - 40.5 + 27 = 0$$
8. **Summary:** The graph starts at (0,0), rises to a local maximum near $$x=1.268$$, then decreases back to (3,0). The curve is smooth and continuous.
9. **Graphing:** Plot the function $$A(x)$$ on $$[0,3]$$ showing the turning point at $$x=3 - \sqrt{3}$$.
Final answer: The curve of $$A(x) = \frac{1}{2} x^3 - \frac{9}{2} x^2 + 9 x$$ on $$[0,3]$$ starts at zero, rises to a local maximum near $$x=1.268$$, then falls back to zero at $$x=3$$.
Cubic Curve Eab0A2
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