Question

Using disks or washers, find the volume of the solid obtained by rotating the region bounded by the curves y=x−1 y=0 x=2 and x=5 about the x-axis.

Answer 1

Using disks ...

`V= \pi \int\limits^5_2 {(x-1)^(2)} \, dx =\pi((1)/(3)(5^(3)-2^(3))-(5^(2)-2^(2))+(5-2))=21\pi`

The volume is 21π units³ ≈ 65.97 units³