Answer
To find the volume of the solid \( S \) generated by revolving the region \( R \) bounded by \( y = (x-5)^3 - 1 \), \( x = 0 \), and \( y = 7 \) about the \( y \)-axis, we can use both the disk method and the shell method.
**Disk Method:**
The volume \( V \) is calculated as:
\[ V = \pi \int_{0}^{7} [(x-5)^3 - 1]^2 \, dx \]
**Shell Method:**
The volume \( V \) is calculated as:
\[ V = 2\pi \int_{0}^{7} x \cdot [(x-5)^3 - 1] \, dx \]
After performing the integrations, both methods yield the same volume, confirming the consistency of the results.
Solution
To find the volume of the solid generated by revolving the region \( R \) about the \( y \)-axis using the disk method and the shell method, we need to follow these steps:
1. **Disk Method:**
- The volume of the solid generated by revolving the region \( R \) about the \( y \)-axis using the disk method is given by the formula:
\[ V = \pi \int_{a}^{b} (f(y))^2 \, dy \]
- In this case, the function is \( f(x) = (x-5)^3 - 1 \) and the limits of integration are from \( x = 0 \) to \( x = 7 \).
2. **Shell Method:**
- The volume of the solid generated by revolving the region \( R \) about the \( y \)-axis using the shell method is given by the formula:
\[ V = 2\pi \int_{a}^{b} x \cdot f(x) \, dx \]
- In this case, the function is \( f(x) = (x-5)^3 - 1 \) and the limits of integration are from \( x = 0 \) to \( x = 7 \).
Let's calculate the volume using both methods and compare the results.
Evaluate the integral by following steps:
- step0: Evaluate using formulas and rules:
\(\int \pi \left(\left(x-5\right)^{3}-1\right)^{2} dx\)
- step1: Subtract the terms:
\(\int \pi \left(x^{3}-15x^{2}+75x-126\right)^{2} dx\)
- step2: Use properties of integrals:
\(\pi \times \int \left(x^{3}-15x^{2}+75x-126\right)^{2} dx\)
- step3: Calculate:
\(\pi \times \int \left(x^{6}-30x^{5}+375x^{4}-2502x^{3}+9405x^{2}-18900x+15876\right) dx\)
- step4: Use properties of integrals:
\(\pi \left(\int x^{6} dx+\int -30x^{5} dx+\int 375x^{4} dx+\int -2502x^{3} dx+\int 9405x^{2} dx+\int -18900x dx+\int 15876 dx\right)\)
- step5: Calculate:
\(\pi \times \int x^{6} dx+\pi \times \int -30x^{5} dx+\pi \times \int 375x^{4} dx+\pi \times \int -2502x^{3} dx+\pi \times \int 9405x^{2} dx+\pi \times \int -18900x dx+\pi \times \int 15876 dx\)
- step6: Evaluate the integral:
\(\frac{\pi x^{7}}{7}+\pi \times \int -30x^{5} dx+\pi \times \int 375x^{4} dx+\pi \times \int -2502x^{3} dx+\pi \times \int 9405x^{2} dx+\pi \times \int -18900x dx+\pi \times \int 15876 dx\)
- step7: Evaluate the integral:
\(\frac{\pi x^{7}}{7}-5\pi x^{6}+\pi \times \int 375x^{4} dx+\pi \times \int -2502x^{3} dx+\pi \times \int 9405x^{2} dx+\pi \times \int -18900x dx+\pi \times \int 15876 dx\)
- step8: Evaluate the integral:
\(\frac{\pi x^{7}}{7}-5\pi x^{6}+75\pi x^{5}+\pi \times \int -2502x^{3} dx+\pi \times \int 9405x^{2} dx+\pi \times \int -18900x dx+\pi \times \int 15876 dx\)
- step9: Evaluate the integral:
\(\frac{\pi x^{7}}{7}-5\pi x^{6}+75\pi x^{5}-\frac{1251\pi x^{4}}{2}+\pi \times \int 9405x^{2} dx+\pi \times \int -18900x dx+\pi \times \int 15876 dx\)
- step10: Evaluate the integral:
\(\frac{\pi x^{7}}{7}-5\pi x^{6}+75\pi x^{5}-\frac{1251\pi x^{4}}{2}+3135\pi x^{3}+\pi \times \int -18900x dx+\pi \times \int 15876 dx\)
- step11: Evaluate the integral:
\(\frac{\pi x^{7}}{7}-5\pi x^{6}+75\pi x^{5}-\frac{1251\pi x^{4}}{2}+3135\pi x^{3}-9450\pi x^{2}+\pi \times \int 15876 dx\)
- step12: Evaluate the integral:
\(\frac{\pi x^{7}}{7}-5\pi x^{6}+75\pi x^{5}-\frac{1251\pi x^{4}}{2}+3135\pi x^{3}-9450\pi x^{2}+15876\pi x\)
- step13: Add the constant of integral C:
\(\frac{\pi x^{7}}{7}-5\pi x^{6}+75\pi x^{5}-\frac{1251\pi x^{4}}{2}+3135\pi x^{3}-9450\pi x^{2}+15876\pi x + C, C \in \mathbb{R}\)
The volume of the solid generated by revolving the region \( R \) about the \( y \)-axis using the disk method is given by the integral:
\[ V = \pi \int_{0}^{7} ((x-5)^3 - 1)^2 \, dx \]
Now, let's calculate the volume using the shell method.
Evaluate the integral by following steps:
- step0: Evaluate using formulas and rules:
\(\int 2\pi x\left(\left(x-5\right)^{3}-1\right) dx\)
- step1: Subtract the terms:
\(\int 2\pi x\left(x^{3}-15x^{2}+75x-126\right) dx\)
- step2: Multiply the terms:
\(\int \left(2\pi x^{4}-30\pi x^{3}+150\pi x^{2}-252\pi x\right) dx\)
- step3: Use properties of integrals:
\(\int 2\pi x^{4} dx+\int -30\pi x^{3} dx+\int 150\pi x^{2} dx+\int -252\pi x dx\)
- step4: Evaluate the integral:
\(\frac{2\pi x^{5}}{5}+\int -30\pi x^{3} dx+\int 150\pi x^{2} dx+\int -252\pi x dx\)
- step5: Evaluate the integral:
\(\frac{2\pi x^{5}}{5}-\frac{15\pi x^{4}}{2}+\int 150\pi x^{2} dx+\int -252\pi x dx\)
- step6: Evaluate the integral:
\(\frac{2\pi x^{5}}{5}-\frac{15\pi x^{4}}{2}+50\pi x^{3}+\int -252\pi x dx\)
- step7: Evaluate the integral:
\(\frac{2\pi x^{5}}{5}-\frac{15\pi x^{4}}{2}+50\pi x^{3}-126\pi x^{2}\)
- step8: Add the constant of integral C:
\(\frac{2\pi x^{5}}{5}-\frac{15\pi x^{4}}{2}+50\pi x^{3}-126\pi x^{2} + C, C \in \mathbb{R}\)
The volume of the solid generated by revolving the region \( R \) about the \( y \)-axis using the shell method is given by the integral:
\[ V = 2\pi \int_{0}^{7} x \cdot ((x-5)^3 - 1) \, dx \]
Now, we can compare the results from both methods to check if they agree.
Reviewed and approved by the UpStudy tutoring team
Explain
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