Find the volume of the solid obtained by rotating the region enclosed by the graphs y = x^2, y = x^(1/2) about the line x = -3. (Use symbolic notation and fractions where needed.)

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Understand the Problem

The question is asking to find the volume of a solid obtained by rotating the area enclosed by the curves y = x^2 and y = x^(1/2) around the line x = -3. This involves setting up an integral to calculate the volume of revolution.

Answer

The volume of the solid is $$ V = \frac{23\pi}{10} $$
Answer for screen readers

The volume of the solid is

$$ V = \frac{23\pi}{10} $$

Steps to Solve

  1. Find Points of Intersection

To determine the enclosed area, find where the curves intersect by setting them equal to each other:

$$ x^2 = x^{1/2} $$

Solve for $x$:

$$ x^2 - x^{1/2} = 0 $$

Factoring gives:

$$ x^{1/2}(x^{3/2} - 1) = 0 $$

This leads to solutions $x = 0$ and $x = 1$.

  1. Sketch the Region

Identify the region bounded by the curves $y = x^2$ and $y = x^{1/2}$ between $x = 0$ and $x = 1$. The top curve is $y = x^{1/2}$ and the bottom curve is $y = x^2$.

  1. Set Up the Volume Integral

Since we are rotating around the line $x = -3$, we'll use the shell method. The formula for volume using shell method is:

$$ V = 2\pi \int_{a}^{b} (radius)(height),dx $$

Here, the radius is $|x + 3|$ and the height is $x^{1/2} - x^2$:

$$ V = 2\pi \int_0^1 (x + 3)(x^{1/2} - x^2) ,dx $$

  1. Integrate the Function

Now we need to compute the integral:

$$ V = 2\pi \int_0^1 (x + 3)(x^{1/2} - x^2) ,dx $$

Expand the integrand:

$$ (x + 3)(x^{1/2} - x^2) = x^{3/2} - x^3 + 3x^{1/2} - 3x^2 $$

Therefore,

$$ V = 2\pi \int_0^1 (x^{3/2} - x^3 + 3x^{1/2} - 3x^2) ,dx $$

  1. Compute Each Integral

Now, compute the integral term by term:

$$ \int x^{3/2} ,dx = \frac{2}{5} x^{5/2} $$

$$ \int x^3 ,dx = \frac{1}{4} x^4 $$

$$ \int x^{1/2} ,dx = \frac{2}{3} x^{3/2} $$

$$ \int x^2 ,dx = \frac{1}{3} x^3 $$

Evaluating the definite integrals from 0 to 1 gives:

$$ \left[ \frac{2}{5}(1)^{5/2} - \frac{1}{4}(1)^4 + 3\left(\frac{2}{3}(1)^{3/2}\right) - 3\left(\frac{1}{3}(1)^3\right) \right] $$

Which simplifies to:

$$ \frac{2}{5} - \frac{1}{4} + 2 - 1 = \frac{2}{5} - \frac{1}{4} + 1 $$

  1. Calculate Volume

Combine the results and multiply by $2\pi$:

$$ V = 2\pi \left( \frac{2}{5} - \frac{1}{4} + 1 \right) $$

Convert to a common denominator to simplify:

Common denominator for 5, 4 is 20, hence:

$$ V = 2\pi \left( \frac{8}{20} - \frac{5}{20} + \frac{20}{20} \right) $$

$$ V = 2\pi \left( \frac{23}{20} \right) $$

Finally, compute:

$$ V = \frac{46\pi}{20} = \frac{23\pi}{10} $$

The volume of the solid is

$$ V = \frac{23\pi}{10} $$

More Information

The volume obtained represents the space occupied by the solid after rotating the region defined by the two curves around the vertical line $x = -3$. This method utilizes calculus principles and the concept of revolving areas to find the volume of solids.

Tips

  • Neglecting to find the points of intersection correctly can lead to the wrong limits of integration.
  • Incorrectly applying the shell method and forgetting to consider the correct radius can result in an incorrect volume.

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