1. **State the problem:** We need to evaluate the definite integral $$\int_1^{10} \frac{2624}{x^2 + x + 1} \, dx$$.
2. **Recall the formula and method:** To integrate a rational function with a quadratic denominator, complete the square in the denominator.
3. **Complete the square:**
$$x^2 + x + 1 = \left(x + \frac{1}{2}\right)^2 + 1 - \frac{1}{4} = \left(x + \frac{1}{2}\right)^2 + \frac{3}{4}$$
4. **Rewrite the integral:**
$$\int_1^{10} \frac{2624}{\left(x + \frac{1}{2}\right)^2 + \left(\frac{\sqrt{3}}{2}\right)^2} \, dx$$
5. **Use substitution:** Let $$u = x + \frac{1}{2}$$, so $$du = dx$$.
6. **Change limits:** When $$x=1$$, $$u=1 + \frac{1}{2} = \frac{3}{2}$$; when $$x=10$$, $$u=10 + \frac{1}{2} = \frac{21}{2}$$.
7. **Integral becomes:**
$$\int_{\frac{3}{2}}^{\frac{21}{2}} \frac{2624}{u^2 + \left(\frac{\sqrt{3}}{2}\right)^2} \, du$$
8. **Recall the integral formula:**
$$\int \frac{1}{u^2 + a^2} du = \frac{1}{a} \arctan\left(\frac{u}{a}\right) + C$$
9. **Apply the formula:** Here, $$a = \frac{\sqrt{3}}{2}$$, so
$$\int_{\frac{3}{2}}^{\frac{21}{2}} \frac{2624}{u^2 + a^2} du = 2624 \times \frac{1}{a} \left[ \arctan\left(\frac{u}{a}\right) \right]_{\frac{3}{2}}^{\frac{21}{2}}$$
10. **Calculate:**
$$= 2624 \times \frac{1}{\frac{\sqrt{3}}{2}} \left( \arctan\left( \frac{\frac{21}{2}}{\frac{\sqrt{3}}{2}} \right) - \arctan\left( \frac{\frac{3}{2}}{\frac{\sqrt{3}}{2}} \right) \right)$$
11. **Simplify the fractions inside arctan:**
$$\frac{\frac{21}{2}}{\frac{\sqrt{3}}{2}} = \frac{21}{\sqrt{3}} = 7 \sqrt{3}$$
$$\frac{\frac{3}{2}}{\frac{\sqrt{3}}{2}} = \frac{3}{\sqrt{3}} = \sqrt{3}$$
12. **Simplify the coefficient:**
$$\frac{1}{\frac{\sqrt{3}}{2}} = \frac{2}{\sqrt{3}}$$
13. **Final expression:**
$$= 2624 \times \frac{2}{\sqrt{3}} \left( \arctan(7 \sqrt{3}) - \arctan(\sqrt{3}) \right)$$
14. **Evaluate arctan values:**
- $$\arctan(\sqrt{3}) = \frac{\pi}{3}$$
- $$\arctan(7 \sqrt{3})$$ is an angle but we leave it as is for exact form.
15. **Therefore, the exact value is:**
$$\boxed{\frac{5248}{\sqrt{3}} \left( \arctan(7 \sqrt{3}) - \frac{\pi}{3} \right)}$$
This is the exact value of the definite integral.
Definite Integral 9Cae27
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