1. **State the problem:** We need to determine the integral of the function $$\frac{x^3+5}{x^2-25}$$ with respect to $x$.
2. **Recall the formula and rules:** To integrate a rational function, we often use polynomial division if the degree of the numerator is greater than or equal to the degree of the denominator, then possibly partial fraction decomposition.
3. **Perform polynomial division:** Divide $x^3 + 5$ by $x^2 - 25$.
$$x^3 + 5 \div x^2 - 25 = x + \frac{25x + 5}{x^2 - 25}$$
4. **Rewrite the integral:**
$$\int \frac{x^3 + 5}{x^2 - 25} dx = \int \left(x + \frac{25x + 5}{x^2 - 25}\right) dx$$
5. **Factor the denominator:**
$$x^2 - 25 = (x - 5)(x + 5)$$
6. **Set up partial fractions for the remaining fraction:**
$$\frac{25x + 5}{(x - 5)(x + 5)} = \frac{A}{x - 5} + \frac{B}{x + 5}$$
Multiply both sides by $(x - 5)(x + 5)$:
$$25x + 5 = A(x + 5) + B(x - 5)$$
7. **Find $A$ and $B$ by substituting values:**
For $x = 5$:
$$25(5) + 5 = A(5 + 5) + B(0) \Rightarrow 125 + 5 = 10A \Rightarrow 130 = 10A \Rightarrow A = 13$$
For $x = -5$:
$$25(-5) + 5 = A(0) + B(-5 - 5) \Rightarrow -125 + 5 = -10B \Rightarrow -120 = -10B \Rightarrow B = 12$$
8. **Rewrite the integral with partial fractions:**
$$\int \left(x + \frac{13}{x - 5} + \frac{12}{x + 5}\right) dx$$
9. **Integrate term by term:**
$$\int x dx + 13 \int \frac{1}{x - 5} dx + 12 \int \frac{1}{x + 5} dx = \frac{x^2}{2} + 13 \ln|x - 5| + 12 \ln|x + 5| + C$$
10. **Final answer:**
$$\boxed{\frac{x^2}{2} + 13 \ln|x - 5| + 12 \ln|x + 5| + C}$$
Integral Rational 60F138
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