Question

Hello. This is a calc question. For finding the volume of a solid revolving around x = -1 do you add -1 to the equation like this:

integral pi* [f(x) - 1]^2 dx

Thanks :)!

Answer 1

\(x=-1\) is a vertical line, so if you wish to use the disk/washer method you must integrate with respect to \(y\).

Let's check with an example. Let's have \(f(x)\) be as shown in the picture, and you want the region bounded by this curve and the axes: