1. **Problem Statement:** We are given the cubic function $$f(x) = \frac{1}{3}x^{3} - \frac{1}{2}x^{2} - 6x + 1$$ and asked to evaluate or approximate the value of $$f\left(\frac{2019}{2003}\right)$$ which is approximately $$10^{-3}$$. We also have a point $$x_0 = 1$$.
2. **Understanding the function:** This is a cubic polynomial function. To evaluate it at any point, substitute the value of $$x$$ into the formula and simplify.
3. **Substitution:** Substitute $$x = \frac{2019}{2003}$$ into the function:
$$
f\left(\frac{2019}{2003}\right) = \frac{1}{3} \left(\frac{2019}{2003}\right)^3 - \frac{1}{2} \left(\frac{2019}{2003}\right)^2 - 6 \left(\frac{2019}{2003}\right) + 1
$$
4. **Approximate powers:** Since $$\frac{2019}{2003} \approx 1.00799$$ (a value slightly greater than 1), we can approximate powers:
- $$\left(1.00799\right)^3 \approx 1.024$$
- $$\left(1.00799\right)^2 \approx 1.016$$
5. **Calculate each term:**
- $$\frac{1}{3} \times 1.024 \approx 0.3413$$
- $$-\frac{1}{2} \times 1.016 \approx -0.508$$
- $$-6 \times 1.00799 \approx -6.048$$
- $$+1$$ remains as is.
6. **Sum all terms:**
$$
0.3413 - 0.508 - 6.048 + 1 = (0.3413 - 0.508) + (1 - 6.048) = -0.1667 - 5.048 = -5.2147
$$
7. **Reconsider approximation:** The problem states $$f\left(\frac{2019}{2003}\right) \approx 10^{-3}$$ which is about 0.001, but our rough calculation gave about -5.21. This suggests the problem might be referring to the difference $$f\left(\frac{2019}{2003}\right) - f(1)$$ or a linear approximation near $$x_0=1$$.
8. **Calculate $$f(1)$$:**
$$
f(1) = \frac{1}{3} (1)^3 - \frac{1}{2} (1)^2 - 6(1) + 1 = \frac{1}{3} - \frac{1}{2} - 6 + 1 = 0.3333 - 0.5 - 6 + 1 = -5.1667
$$
9. **Difference:**
$$
f\left(\frac{2019}{2003}\right) - f(1) \approx -5.2147 - (-5.1667) = -0.048$$
10. **Linear approximation (using derivative):**
- Derivative:
$$
f'(x) = \frac{d}{dx} \left( \frac{1}{3}x^3 - \frac{1}{2}x^2 - 6x + 1 \right) = x^2 - x - 6
$$
- Evaluate at $$x_0=1$$:
$$
f'(1) = 1^2 - 1 - 6 = 1 - 1 - 6 = -6
$$
- Approximate change:
$$
\Delta x = \frac{2019}{2003} - 1 = \frac{2019 - 2003}{2003} = \frac{16}{2003} \approx 0.00799
$$
- Linear approximation:
$$
f\left(\frac{2019}{2003}\right) \approx f(1) + f'(1) \times \Delta x = -5.1667 + (-6)(0.00799) = -5.1667 - 0.0479 = -5.2146
$$
This matches the direct substitution result.
11. **Conclusion:** The value $$f\left(\frac{2019}{2003}\right)$$ is approximately $$-5.2146$$, not $$10^{-3}$$. The given approximation $$10^{-3}$$ might refer to a different context or error term.
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**Final answer:** $$f\left(\frac{2019}{2003}\right) \approx -5.2146$$
Cubic Function Evaluation
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