Volume of Revolution: Find the Volume from y = x+6 & y = x^2 - 4x

In summary, the question asks to find the volume of the solid generated when the area enclosed by the line y = x + 6 and the curve y = x^2 - 4x is rotated 360 degrees about the x-axis. The intersections of the line and curve are located at x = -1 and x = 6, in the first, second, and fourth quadrants. It is unclear how the region in the fourth quadrant will contribute to the volume, as it may overlap with the region in the first quadrant.
  • #1
songoku
2,306
327

Homework Statement


The line y = x + 6 meets the curve y = x2-4x at the points P and Q. Find the volume of the solid generated when the area enclosed by the line and the curve is rotated through 360o about the x-axis


Homework Equations


Integration


The Attempt at a Solution


I've drawn the graph and found the intersections, which are x = -1 and x = 6. The region are located in first, second, and fourth quadrants. I'm confused about the region in fourth quadrant.
How to find the volume of all the region when they are rotated 360o about the x-axis? I can't imagine what shape it forms, I think the region in fourth quadrant will "overlap" with region in first quadrant when rotated.

Thanks
 
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  • #2
hi songoku! :smile:

yes, you're right … that doesn't make sense :redface:

is that the whole question? I'm wondering why they bothered to give points P and Q names :confused:
 
  • #3
tiny-tim said:
hi songoku! :smile:

yes, you're right … that doesn't make sense :redface:

is that the whole question? I'm wondering why they bothered to give points P and Q names :confused:

hi tiny-tim! :smile:

Yes, that's the whole question. I just noticed that we don't need P and Q, just say "the area enclosed by the line and the curve" is enough.

For now, let's assume there is mistake in the question :biggrin:

Thanks tiny-tim!
 

Related to Volume of Revolution: Find the Volume from y = x+6 & y = x^2 - 4x

What is the volume of revolution for the given equations?

The volume of revolution is the total volume formed by rotating a region bounded by two curves about a given axis. In this case, the region is bounded by the curves y = x+6 and y = x^2 - 4x, and the axis of rotation is the x-axis.

What is the method for finding the volume of revolution?

The volume of revolution can be found using the formula V = π∫(R(x))^2 dx, where R(x) is the radius at a given x-value and the integral is taken over the interval of rotation.

Can the volume of revolution be negative?

No, the volume of revolution is always a positive value since it represents a physical space and cannot have negative measurements.

How do I determine the limits of integration for finding the volume of revolution?

The limits of integration can be determined by finding the x-values where the two curves intersect. These points will be the upper and lower limits of integration.

Can the volume of revolution be calculated for other axes of rotation?

Yes, the volume of revolution can be calculated for any axis of rotation. The formula remains the same, but the limits of integration and radius function may change depending on the axis of rotation.

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