find the volume generated by revolving the area bounded by y=-x^3, y=0, and x=-2 about the line x=1.

I know how to the solve the problem but am not sure how to get the interval. Please help.

1 answer

Well, if you graph things, you have a curved triangular region with vertices at (-2,8),(-2,0),(0,0).

So, using shells of thickness dx, you have the area as

∫[-2,0] 2πrh dx
where
r = 1-x
h = y = -x^3

using washers of thickness dy, you have

∫[0,8] π(R^2-r^2) dy
where
R = 1+2
r = 1+x = 1+∛y