1. **Problem statement:** Find the volume of the solid formed by rotating the region under the curve $$y=\frac{5}{x^2+5x+6}$$ from $$x=0$$ to $$x=1$$ about the x-axis.
2. **Formula for volume about the x-axis:**
$$V=\pi \int_a^b [f(x)]^2 dx$$
This formula calculates the volume of a solid of revolution by integrating the square of the function times $$\pi$$ over the interval.
3. **Rewrite the function:**
Factor the denominator:
$$x^2+5x+6=(x+2)(x+3)$$
So,
$$y=\frac{5}{(x+2)(x+3)}$$
4. **Set up the integral:**
$$V=\pi \int_0^1 \left(\frac{5}{(x+2)(x+3)}\right)^2 dx=25\pi \int_0^1 \frac{1}{(x+2)^2 (x+3)^2} dx$$
5. **Partial fraction decomposition:**
We want to express
$$\frac{1}{(x+2)^2 (x+3)^2} = \frac{A}{x+2} + \frac{B}{(x+2)^2} + \frac{C}{x+3} + \frac{D}{(x+3)^2}$$
Multiply both sides by $$ (x+2)^2 (x+3)^2 $$:
$$1 = A(x+2)(x+3)^2 + B(x+3)^2 + C(x+3)(x+2)^2 + D(x+2)^2$$
6. **Find coefficients by substituting values:**
- Let $$x=-2$$:
$$1 = B(1)^2 = B \Rightarrow B=1$$
- Let $$x=-3$$:
$$1 = D( -1)^2 = D \Rightarrow D=1$$
7. **Expand and equate coefficients:**
Expand terms and equate coefficients of powers of $$x$$ to solve for $$A$$ and $$C$$:
After simplification, we find:
$$A = -1, \quad C = -1$$
8. **Rewrite the integral:**
$$\int_0^1 \frac{1}{(x+2)^2 (x+3)^2} dx = \int_0^1 \left( \frac{-1}{x+2} + \frac{1}{(x+2)^2} - \frac{1}{x+3} + \frac{1}{(x+3)^2} \right) dx$$
9. **Integrate term by term:**
- $$\int \frac{1}{(x+a)^2} dx = -\frac{1}{x+a} + C$$
- $$\int \frac{1}{x+a} dx = \ln|x+a| + C$$
So,
$$\int_0^1 \frac{-1}{x+2} dx = -[\ln(x+2)]_0^1 = -\ln 3 + \ln 2$$
$$\int_0^1 \frac{1}{(x+2)^2} dx = \left[-\frac{1}{x+2}\right]_0^1 = -\frac{1}{3} + \frac{1}{2} = \frac{1}{6}$$
$$\int_0^1 \frac{-1}{x+3} dx = -[\ln(x+3)]_0^1 = -\ln 4 + \ln 3$$
$$\int_0^1 \frac{1}{(x+3)^2} dx = \left[-\frac{1}{x+3}\right]_0^1 = -\frac{1}{4} + \frac{1}{3} = \frac{1}{12}$$
10. **Sum all integrals:**
$$I = (-\ln 3 + \ln 2) + \frac{1}{6} + (-\ln 4 + \ln 3) + \frac{1}{12} = (\ln 2 - \ln 4) + \left(\frac{1}{6} + \frac{1}{12}\right)$$
Since $$\ln 4 = \ln 2^2 = 2 \ln 2$$,
$$\ln 2 - \ln 4 = \ln 2 - 2 \ln 2 = -\ln 2$$
And $$\frac{1}{6} + \frac{1}{12} = \frac{2}{12} + \frac{1}{12} = \frac{3}{12} = \frac{1}{4}$$
So,
$$I = -\ln 2 + \frac{1}{4}$$
11. **Calculate volume:**
$$V = 25 \pi I = 25 \pi \left(-\ln 2 + \frac{1}{4}\right) = 25 \pi \left(\frac{1}{4} - \ln 2\right)$$
**Final answer:**
$$\boxed{V = 25 \pi \left(\frac{1}{4} - \ln 2\right)}$$
Volume X Axis 52210A
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